Re: P0303 cylinder #3 misfire
 

Carl wrote:
> agreed.
>
> "billy ray" wrote ...
>> If a coil was bad then two cylinders
>> (3 and 4) would be misfiring.

It can also be the rail. I've seen where
the rail has failed internally and that was
causing the misfire.

--
DougW

Re: P0303 cylinder #3 misfire
 

Carl wrote:
> agreed.
>
> "billy ray" wrote ...
>> If a coil was bad then two cylinders
>> (3 and 4) would be misfiring.

It can also be the rail. I've seen where
the rail has failed internally and that was
causing the misfire.

--
DougW

Re: P0303 cylinder #3 misfire
 

Carl wrote:
> agreed.
>
> "billy ray" wrote ...
>> If a coil was bad then two cylinders
>> (3 and 4) would be misfiring.

It can also be the rail. I've seen where
the rail has failed internally and that was
causing the misfire.

--
DougW

Re: P0303 cylinder #3 misfire
 

Ok, but for one coil power two cylinders I would think there is one
input connection on the coil to rail and one connection going to each
plug with a connection at each plug, no?

Haven't seen the setup yet.

Mike

bllsht wrote:
>
> A bad connection would kill either 2 or all cylinders.
>
> On Sat, 06 Jan 2007 20:32:50 -0500, Mike Romain <romainm@sympatico.ca>
> wrote:
>
> >Or it's electronic plug and socket are dirty.....
> >
> >Mike
> >
> >Jeff Strickland wrote:
> >>
> >> So, one of the coils is bad.
> >>
> >> "Carl" <carlsaiyed@hotmailREMOVE.com> wrote in message
> >> news:bdqdnb4NANz57QHYnZ2dnUVZ_tOmnZ2d@comcast.com. ..
> >> > Jeff, no plug wires or dist cap on an 00 and 01. Coil rail with three coil
> >> > packs.
> >> >
> >> > Carl
> >> >
> >> >
> >> > "Jeff Strickland" <crwlr@yahoo.com> wrote in message
> >> > news:OfidnY5u3NmnmQHYnZ2dnUVZ_h6jnZ2d@ez2.net...
> >> >> With a misfire, I'd be looking at the plug wires or coil. I'd check plug
> >> >> wires if there was a distributor, or I'd look at the coil if there was a
> >> >> separate coil for each cylinder, or a coil for every two cylinders.
> >> >>
> >> >>
> >> >>
> >> >> "01XJ" <adam.tsacoumangos@gmail.com> wrote in message
> >> >> news:1167779855.090317.153570@v33g2000cwv.googlegr oups.com...
> >> >>>I just started experiencing a rough idle on my 2001 Cherokee (78k
> >> >>> miles). My engine light went on a little after that with the P0303
> >> >>> code. I just replaced the spark plugs, but that didn't help anything.
> >> >>> I was
> >> >>> thinking about changing the ignition coil or fuel injector. One other
> >> >>> possibility I was
> >> >>> thinking was checking the cylinder compression (maybe a gasket leak?).
> >> >>> Anyone have any suggestions?
> >> >>>
> >> >>
> >> >
> >> >

Re: P0303 cylinder #3 misfire
 

Ok, but for one coil power two cylinders I would think there is one
input connection on the coil to rail and one connection going to each
plug with a connection at each plug, no?

Haven't seen the setup yet.

Mike

bllsht wrote:
>
> A bad connection would kill either 2 or all cylinders.
>
> On Sat, 06 Jan 2007 20:32:50 -0500, Mike Romain <romainm@sympatico.ca>
> wrote:
>
> >Or it's electronic plug and socket are dirty.....
> >
> >Mike
> >
> >Jeff Strickland wrote:
> >>
> >> So, one of the coils is bad.
> >>
> >> "Carl" <carlsaiyed@hotmailREMOVE.com> wrote in message
> >> news:bdqdnb4NANz57QHYnZ2dnUVZ_tOmnZ2d@comcast.com. ..
> >> > Jeff, no plug wires or dist cap on an 00 and 01. Coil rail with three coil
> >> > packs.
> >> >
> >> > Carl
> >> >
> >> >
> >> > "Jeff Strickland" <crwlr@yahoo.com> wrote in message
> >> > news:OfidnY5u3NmnmQHYnZ2dnUVZ_h6jnZ2d@ez2.net...
> >> >> With a misfire, I'd be looking at the plug wires or coil. I'd check plug
> >> >> wires if there was a distributor, or I'd look at the coil if there was a
> >> >> separate coil for each cylinder, or a coil for every two cylinders.
> >> >>
> >> >>
> >> >>
> >> >> "01XJ" <adam.tsacoumangos@gmail.com> wrote in message
> >> >> news:1167779855.090317.153570@v33g2000cwv.googlegr oups.com...
> >> >>>I just started experiencing a rough idle on my 2001 Cherokee (78k
> >> >>> miles). My engine light went on a little after that with the P0303
> >> >>> code. I just replaced the spark plugs, but that didn't help anything.
> >> >>> I was
> >> >>> thinking about changing the ignition coil or fuel injector. One other
> >> >>> possibility I was
> >> >>> thinking was checking the cylinder compression (maybe a gasket leak?).
> >> >>> Anyone have any suggestions?
> >> >>>
> >> >>
> >> >
> >> >

Re: P0303 cylinder #3 misfire
 

Ok, but for one coil power two cylinders I would think there is one
input connection on the coil to rail and one connection going to each
plug with a connection at each plug, no?

Haven't seen the setup yet.

Mike

bllsht wrote:
>
> A bad connection would kill either 2 or all cylinders.
>
> On Sat, 06 Jan 2007 20:32:50 -0500, Mike Romain <romainm@sympatico.ca>
> wrote:
>
> >Or it's electronic plug and socket are dirty.....
> >
> >Mike
> >
> >Jeff Strickland wrote:
> >>
> >> So, one of the coils is bad.
> >>
> >> "Carl" <carlsaiyed@hotmailREMOVE.com> wrote in message
> >> news:bdqdnb4NANz57QHYnZ2dnUVZ_tOmnZ2d@comcast.com. ..
> >> > Jeff, no plug wires or dist cap on an 00 and 01. Coil rail with three coil
> >> > packs.
> >> >
> >> > Carl
> >> >
> >> >
> >> > "Jeff Strickland" <crwlr@yahoo.com> wrote in message
> >> > news:OfidnY5u3NmnmQHYnZ2dnUVZ_h6jnZ2d@ez2.net...
> >> >> With a misfire, I'd be looking at the plug wires or coil. I'd check plug
> >> >> wires if there was a distributor, or I'd look at the coil if there was a
> >> >> separate coil for each cylinder, or a coil for every two cylinders.
> >> >>
> >> >>
> >> >>
> >> >> "01XJ" <adam.tsacoumangos@gmail.com> wrote in message
> >> >> news:1167779855.090317.153570@v33g2000cwv.googlegr oups.com...
> >> >>>I just started experiencing a rough idle on my 2001 Cherokee (78k
> >> >>> miles). My engine light went on a little after that with the P0303
> >> >>> code. I just replaced the spark plugs, but that didn't help anything.
> >> >>> I was
> >> >>> thinking about changing the ignition coil or fuel injector. One other
> >> >>> possibility I was
> >> >>> thinking was checking the cylinder compression (maybe a gasket leak?).
> >> >>> Anyone have any suggestions?
> >> >>>
> >> >>
> >> >
> >> >

Re: P0303 cylinder #3 misfire
 

Mike Romain wrote:
> Ok, but for one coil power two cylinders I would think there is one
> input connection on the coil to rail and one connection going to each
> plug with a connection at each plug, no?

IIRC, five wires.
three ecu grounds, two ecu battery.
Plus and one connection for each plug

http://www.wjjeeps.com/engine/coil_rail_assembly_01.jpg

http://www.motorage.com/motorage/dat...30/article.pdf

--
DougW

Re: P0303 cylinder #3 misfire
 

Mike Romain wrote:
> Ok, but for one coil power two cylinders I would think there is one
> input connection on the coil to rail and one connection going to each
> plug with a connection at each plug, no?

IIRC, five wires.
three ecu grounds, two ecu battery.
Plus and one connection for each plug

http://www.wjjeeps.com/engine/coil_rail_assembly_01.jpg

http://www.motorage.com/motorage/dat...30/article.pdf

--
DougW

Re: P0303 cylinder #3 misfire
 

Mike Romain wrote:
> Ok, but for one coil power two cylinders I would think there is one
> input connection on the coil to rail and one connection going to each
> plug with a connection at each plug, no?

IIRC, five wires.
three ecu grounds, two ecu battery.
Plus and one connection for each plug

http://www.wjjeeps.com/engine/coil_rail_assembly_01.jpg

http://www.motorage.com/motorage/dat...30/article.pdf

--
DougW

Re: P0303 cylinder #3 misfire
 

One connector, 4 wires. 12v in and 3 driver wires.

On Sun, 07 Jan 2007 12:05:11 -0500, Mike Romain <romainm@sympatico.ca>
wrote:

>Ok, but for one coil power two cylinders I would think there is one
>input connection on the coil to rail and one connection going to each
>plug with a connection at each plug, no?
>
>Haven't seen the setup yet.
>
>Mike
>
>bllsht wrote:
>>
>> A bad connection would kill either 2 or all cylinders.
>>
>> On Sat, 06 Jan 2007 20:32:50 -0500, Mike Romain <romainm@sympatico.ca>
>> wrote:
>>
>> >Or it's electronic plug and socket are dirty.....
>> >
>> >Mike
>> >
>> >Jeff Strickland wrote:
>> >>
>> >> So, one of the coils is bad.
>> >>
>> >> "Carl" <carlsaiyed@hotmailREMOVE.com> wrote in message
>> >> news:bdqdnb4NANz57QHYnZ2dnUVZ_tOmnZ2d@comcast.com. ..
>> >> > Jeff, no plug wires or dist cap on an 00 and 01. Coil rail with three coil
>> >> > packs.
>> >> >
>> >> > Carl
>> >> >
>> >> >
>> >> > "Jeff Strickland" <crwlr@yahoo.com> wrote in message
>> >> > news:OfidnY5u3NmnmQHYnZ2dnUVZ_h6jnZ2d@ez2.net...
>> >> >> With a misfire, I'd be looking at the plug wires or coil. I'd check plug
>> >> >> wires if there was a distributor, or I'd look at the coil if there was a
>> >> >> separate coil for each cylinder, or a coil for every two cylinders.
>> >> >>
>> >> >>
>> >> >>
>> >> >> "01XJ" <adam.tsacoumangos@gmail.com> wrote in message
>> >> >> news:1167779855.090317.153570@v33g2000cwv.googlegr oups.com...
>> >> >>>I just started experiencing a rough idle on my 2001 Cherokee (78k
>> >> >>> miles). My engine light went on a little after that with the P0303
>> >> >>> code. I just replaced the spark plugs, but that didn't help anything.
>> >> >>> I was
>> >> >>> thinking about changing the ignition coil or fuel injector. One other
>> >> >>> possibility I was
>> >> >>> thinking was checking the cylinder compression (maybe a gasket leak?).
>> >> >>> Anyone have any suggestions?
>> >> >>>
>> >> >>
>> >> >
>> >> >

Re: P0303 cylinder #3 misfire
 

One connector, 4 wires. 12v in and 3 driver wires.

On Sun, 07 Jan 2007 12:05:11 -0500, Mike Romain <romainm@sympatico.ca>
wrote:

>Ok, but for one coil power two cylinders I would think there is one
>input connection on the coil to rail and one connection going to each
>plug with a connection at each plug, no?
>
>Haven't seen the setup yet.
>
>Mike
>
>bllsht wrote:
>>
>> A bad connection would kill either 2 or all cylinders.
>>
>> On Sat, 06 Jan 2007 20:32:50 -0500, Mike Romain <romainm@sympatico.ca>
>> wrote:
>>
>> >Or it's electronic plug and socket are dirty.....
>> >
>> >Mike
>> >
>> >Jeff Strickland wrote:
>> >>
>> >> So, one of the coils is bad.
>> >>
>> >> "Carl" <carlsaiyed@hotmailREMOVE.com> wrote in message
>> >> news:bdqdnb4NANz57QHYnZ2dnUVZ_tOmnZ2d@comcast.com. ..
>> >> > Jeff, no plug wires or dist cap on an 00 and 01. Coil rail with three coil
>> >> > packs.
>> >> >
>> >> > Carl
>> >> >
>> >> >
>> >> > "Jeff Strickland" <crwlr@yahoo.com> wrote in message
>> >> > news:OfidnY5u3NmnmQHYnZ2dnUVZ_h6jnZ2d@ez2.net...
>> >> >> With a misfire, I'd be looking at the plug wires or coil. I'd check plug
>> >> >> wires if there was a distributor, or I'd look at the coil if there was a
>> >> >> separate coil for each cylinder, or a coil for every two cylinders.
>> >> >>
>> >> >>
>> >> >>
>> >> >> "01XJ" <adam.tsacoumangos@gmail.com> wrote in message
>> >> >> news:1167779855.090317.153570@v33g2000cwv.googlegr oups.com...
>> >> >>>I just started experiencing a rough idle on my 2001 Cherokee (78k
>> >> >>> miles). My engine light went on a little after that with the P0303
>> >> >>> code. I just replaced the spark plugs, but that didn't help anything.
>> >> >>> I was
>> >> >>> thinking about changing the ignition coil or fuel injector. One other
>> >> >>> possibility I was
>> >> >>> thinking was checking the cylinder compression (maybe a gasket leak?).
>> >> >>> Anyone have any suggestions?
>> >> >>>
>> >> >>
>> >> >
>> >> >

Re: P0303 cylinder #3 misfire
 

One connector, 4 wires. 12v in and 3 driver wires.

On Sun, 07 Jan 2007 12:05:11 -0500, Mike Romain <romainm@sympatico.ca>
wrote:

>Ok, but for one coil power two cylinders I would think there is one
>input connection on the coil to rail and one connection going to each
>plug with a connection at each plug, no?
>
>Haven't seen the setup yet.
>
>Mike
>
>bllsht wrote:
>>
>> A bad connection would kill either 2 or all cylinders.
>>
>> On Sat, 06 Jan 2007 20:32:50 -0500, Mike Romain <romainm@sympatico.ca>
>> wrote:
>>
>> >Or it's electronic plug and socket are dirty.....
>> >
>> >Mike
>> >
>> >Jeff Strickland wrote:
>> >>
>> >> So, one of the coils is bad.
>> >>
>> >> "Carl" <carlsaiyed@hotmailREMOVE.com> wrote in message
>> >> news:bdqdnb4NANz57QHYnZ2dnUVZ_tOmnZ2d@comcast.com. ..
>> >> > Jeff, no plug wires or dist cap on an 00 and 01. Coil rail with three coil
>> >> > packs.
>> >> >
>> >> > Carl
>> >> >
>> >> >
>> >> > "Jeff Strickland" <crwlr@yahoo.com> wrote in message
>> >> > news:OfidnY5u3NmnmQHYnZ2dnUVZ_h6jnZ2d@ez2.net...
>> >> >> With a misfire, I'd be looking at the plug wires or coil. I'd check plug
>> >> >> wires if there was a distributor, or I'd look at the coil if there was a
>> >> >> separate coil for each cylinder, or a coil for every two cylinders.
>> >> >>
>> >> >>
>> >> >>
>> >> >> "01XJ" <adam.tsacoumangos@gmail.com> wrote in message
>> >> >> news:1167779855.090317.153570@v33g2000cwv.googlegr oups.com...
>> >> >>>I just started experiencing a rough idle on my 2001 Cherokee (78k
>> >> >>> miles). My engine light went on a little after that with the P0303
>> >> >>> code. I just replaced the spark plugs, but that didn't help anything.
>> >> >>> I was
>> >> >>> thinking about changing the ignition coil or fuel injector. One other
>> >> >>> possibility I was
>> >> >>> thinking was checking the cylinder compression (maybe a gasket leak?).
>> >> >>> Anyone have any suggestions?
>> >> >>>
>> >> >>
>> >> >
>> >> >

Re: P0303 cylinder #3 misfire
 

What connects the spark plugs to this pack?

Thanks,

Mike

bllsht wrote:
>
> One connector, 4 wires. 12v in and 3 driver wires.
>
> On Sun, 07 Jan 2007 12:05:11 -0500, Mike Romain <romainm@sympatico.ca>
> wrote:
>
> >Ok, but for one coil power two cylinders I would think there is one
> >input connection on the coil to rail and one connection going to each
> >plug with a connection at each plug, no?
> >
> >Haven't seen the setup yet.
> >
> >Mike
> >
> >bllsht wrote:
> >>
> >> A bad connection would kill either 2 or all cylinders.
> >>
> >> On Sat, 06 Jan 2007 20:32:50 -0500, Mike Romain <romainm@sympatico.ca>
> >> wrote:
> >>
> >> >Or it's electronic plug and socket are dirty.....
> >> >
> >> >Mike
> >> >
> >> >Jeff Strickland wrote:
> >> >>
> >> >> So, one of the coils is bad.
> >> >>
> >> >> "Carl" <carlsaiyed@hotmailREMOVE.com> wrote in message
> >> >> news:bdqdnb4NANz57QHYnZ2dnUVZ_tOmnZ2d@comcast.com. ..
> >> >> > Jeff, no plug wires or dist cap on an 00 and 01. Coil rail with three coil
> >> >> > packs.
> >> >> >
> >> >> > Carl
> >> >> >
> >> >> >
> >> >> > "Jeff Strickland" <crwlr@yahoo.com> wrote in message
> >> >> > news:OfidnY5u3NmnmQHYnZ2dnUVZ_h6jnZ2d@ez2.net...
> >> >> >> With a misfire, I'd be looking at the plug wires or coil. I'd check plug
> >> >> >> wires if there was a distributor, or I'd look at the coil if there was a
> >> >> >> separate coil for each cylinder, or a coil for every two cylinders.
> >> >> >>
> >> >> >>
> >> >> >>
> >> >> >> "01XJ" <adam.tsacoumangos@gmail.com> wrote in message
> >> >> >> news:1167779855.090317.153570@v33g2000cwv.googlegr oups.com...
> >> >> >>>I just started experiencing a rough idle on my 2001 Cherokee (78k
> >> >> >>> miles). My engine light went on a little after that with the P0303
> >> >> >>> code. I just replaced the spark plugs, but that didn't help anything.
> >> >> >>> I was
> >> >> >>> thinking about changing the ignition coil or fuel injector. One other
> >> >> >>> possibility I was
> >> >> >>> thinking was checking the cylinder compression (maybe a gasket leak?).
> >> >> >>> Anyone have any suggestions?
> >> >> >>>
> >> >> >>
> >> >> >
> >> >> >

Re: P0303 cylinder #3 misfire
 

What connects the spark plugs to this pack?

Thanks,

Mike

bllsht wrote:
>
> One connector, 4 wires. 12v in and 3 driver wires.
>
> On Sun, 07 Jan 2007 12:05:11 -0500, Mike Romain <romainm@sympatico.ca>
> wrote:
>
> >Ok, but for one coil power two cylinders I would think there is one
> >input connection on the coil to rail and one connection going to each
> >plug with a connection at each plug, no?
> >
> >Haven't seen the setup yet.
> >
> >Mike
> >
> >bllsht wrote:
> >>
> >> A bad connection would kill either 2 or all cylinders.
> >>
> >> On Sat, 06 Jan 2007 20:32:50 -0500, Mike Romain <romainm@sympatico.ca>
> >> wrote:
> >>
> >> >Or it's electronic plug and socket are dirty.....
> >> >
> >> >Mike
> >> >
> >> >Jeff Strickland wrote:
> >> >>
> >> >> So, one of the coils is bad.
> >> >>
> >> >> "Carl" <carlsaiyed@hotmailREMOVE.com> wrote in message
> >> >> news:bdqdnb4NANz57QHYnZ2dnUVZ_tOmnZ2d@comcast.com. ..
> >> >> > Jeff, no plug wires or dist cap on an 00 and 01. Coil rail with three coil
> >> >> > packs.
> >> >> >
> >> >> > Carl
> >> >> >
> >> >> >
> >> >> > "Jeff Strickland" <crwlr@yahoo.com> wrote in message
> >> >> > news:OfidnY5u3NmnmQHYnZ2dnUVZ_h6jnZ2d@ez2.net...
> >> >> >> With a misfire, I'd be looking at the plug wires or coil. I'd check plug
> >> >> >> wires if there was a distributor, or I'd look at the coil if there was a
> >> >> >> separate coil for each cylinder, or a coil for every two cylinders.
> >> >> >>
> >> >> >>
> >> >> >>
> >> >> >> "01XJ" <adam.tsacoumangos@gmail.com> wrote in message
> >> >> >> news:1167779855.090317.153570@v33g2000cwv.googlegr oups.com...
> >> >> >>>I just started experiencing a rough idle on my 2001 Cherokee (78k
> >> >> >>> miles). My engine light went on a little after that with the P0303
> >> >> >>> code. I just replaced the spark plugs, but that didn't help anything.
> >> >> >>> I was
> >> >> >>> thinking about changing the ignition coil or fuel injector. One other
> >> >> >>> possibility I was
> >> >> >>> thinking was checking the cylinder compression (maybe a gasket leak?).
> >> >> >>> Anyone have any suggestions?
> >> >> >>>
> >> >> >>
> >> >> >
> >> >> >

Re: P0303 cylinder #3 misfire
 

What connects the spark plugs to this pack?

Thanks,

Mike

bllsht wrote:
>
> One connector, 4 wires. 12v in and 3 driver wires.
>
> On Sun, 07 Jan 2007 12:05:11 -0500, Mike Romain <romainm@sympatico.ca>
> wrote:
>
> >Ok, but for one coil power two cylinders I would think there is one
> >input connection on the coil to rail and one connection going to each
> >plug with a connection at each plug, no?
> >
> >Haven't seen the setup yet.
> >
> >Mike
> >
> >bllsht wrote:
> >>
> >> A bad connection would kill either 2 or all cylinders.
> >>
> >> On Sat, 06 Jan 2007 20:32:50 -0500, Mike Romain <romainm@sympatico.ca>
> >> wrote:
> >>
> >> >Or it's electronic plug and socket are dirty.....
> >> >
> >> >Mike
> >> >
> >> >Jeff Strickland wrote:
> >> >>
> >> >> So, one of the coils is bad.
> >> >>
> >> >> "Carl" <carlsaiyed@hotmailREMOVE.com> wrote in message
> >> >> news:bdqdnb4NANz57QHYnZ2dnUVZ_tOmnZ2d@comcast.com. ..
> >> >> > Jeff, no plug wires or dist cap on an 00 and 01. Coil rail with three coil
> >> >> > packs.
> >> >> >
> >> >> > Carl
> >> >> >
> >> >> >
> >> >> > "Jeff Strickland" <crwlr@yahoo.com> wrote in message
> >> >> > news:OfidnY5u3NmnmQHYnZ2dnUVZ_h6jnZ2d@ez2.net...
> >> >> >> With a misfire, I'd be looking at the plug wires or coil. I'd check plug
> >> >> >> wires if there was a distributor, or I'd look at the coil if there was a
> >> >> >> separate coil for each cylinder, or a coil for every two cylinders.
> >> >> >>
> >> >> >>
> >> >> >>
> >> >> >> "01XJ" <adam.tsacoumangos@gmail.com> wrote in message
> >> >> >> news:1167779855.090317.153570@v33g2000cwv.googlegr oups.com...
> >> >> >>>I just started experiencing a rough idle on my 2001 Cherokee (78k
> >> >> >>> miles). My engine light went on a little after that with the P0303
> >> >> >>> code. I just replaced the spark plugs, but that didn't help anything.
> >> >> >>> I was
> >> >> >>> thinking about changing the ignition coil or fuel injector. One other
> >> >> >>> possibility I was
> >> >> >>> thinking was checking the cylinder compression (maybe a gasket leak?).
> >> >> >>> Anyone have any suggestions?
> >> >> >>>
> >> >> >>
> >> >> >
> >> >> >

Re: P0303 cylinder #3 misfire
 

Mike Romain wrote:
> What connects the spark plugs to this pack?

The coil rail.
http://www.4x4xplor.com/coil.html

It looks like the packs are molded into the
rail. That sucks especially if one pack goes bad.

--
DougW

Re: P0303 cylinder #3 misfire
 

Mike Romain wrote:
> What connects the spark plugs to this pack?

The coil rail.
http://www.4x4xplor.com/coil.html

It looks like the packs are molded into the
rail. That sucks especially if one pack goes bad.

--
DougW

Re: P0303 cylinder #3 misfire
 

Mike Romain wrote:
> What connects the spark plugs to this pack?

The coil rail.
http://www.4x4xplor.com/coil.html

It looks like the packs are molded into the
rail. That sucks especially if one pack goes bad.

--
DougW

Re: P0303 cylinder #3 misfire
 

They are connected with plug wires but they are sealed units and
those connections are not accessible, at least on this setup. Still,
one open plug wire would kill 2 cylinders because of the way the
system operates. For each pair of cylinders, one plug is always fired
negatively, and the other positively. That is, one fires from the
center eletrtode to the outer electrode, and the other fires from the
outer to the center. It's a series circuit. Open a series circuit and
no current flows.



On Sun, 07 Jan 2007 15:01:55 -0500, Mike Romain romainm@sympatico.ca>
wrote:

>What connects the spark plugs to this pack?
>
>Thanks,
>
>Mike
>
>bllsht wrote:
>>
>> One connector, 4 wires. 12v in and 3 driver wires.
>>
>> On Sun, 07 Jan 2007 12:05:11 -0500, Mike Romain <romainm@sympatico.ca>
>> wrote:
>>
>> >Ok, but for one coil power two cylinders I would think there is one
>> >input connection on the coil to rail and one connection going to each
>> >plug with a connection at each plug, no?
>> >
>> >Haven't seen the setup yet.
>> >
>> >Mike
>> >
>> >bllsht wrote:
>> >>
>> >> A bad connection would kill either 2 or all cylinders.
>> >>
>> >> On Sat, 06 Jan 2007 20:32:50 -0500, Mike Romain <romainm@sympatico.ca>
>> >> wrote:
>> >>
>> >> >Or it's electronic plug and socket are dirty.....
>> >> >
>> >> >Mike
>> >> >
>> >> >Jeff Strickland wrote:
>> >> >>
>> >> >> So, one of the coils is bad.
>> >> >>
>> >> >> "Carl" <carlsaiyed@hotmailREMOVE.com> wrote in message
>> >> >> news:bdqdnb4NANz57QHYnZ2dnUVZ_tOmnZ2d@comcast.com. ..
>> >> >> > Jeff, no plug wires or dist cap on an 00 and 01. Coil rail with three coil
>> >> >> > packs.
>> >> >> >
>> >> >> > Carl
>> >> >> >
>> >> >> >
>> >> >> > "Jeff Strickland" <crwlr@yahoo.com> wrote in message
>> >> >> > news:OfidnY5u3NmnmQHYnZ2dnUVZ_h6jnZ2d@ez2.net...
>> >> >> >> With a misfire, I'd be looking at the plug wires or coil. I'd check plug
>> >> >> >> wires if there was a distributor, or I'd look at the coil if there was a
>> >> >> >> separate coil for each cylinder, or a coil for every two cylinders.
>> >> >> >>
>> >> >> >>
>> >> >> >>
>> >> >> >> "01XJ" <adam.tsacoumangos@gmail.com> wrote in message
>> >> >> >> news:1167779855.090317.153570@v33g2000cwv.googlegr oups.com...
>> >> >> >>>I just started experiencing a rough idle on my 2001 Cherokee (78k
>> >> >> >>> miles). My engine light went on a little after that with the P0303
>> >> >> >>> code. I just replaced the spark plugs, but that didn't help anything.
>> >> >> >>> I was
>> >> >> >>> thinking about changing the ignition coil or fuel injector. One other
>> >> >> >>> possibility I was
>> >> >> >>> thinking was checking the cylinder compression (maybe a gasket leak?).
>> >> >> >>> Anyone have any suggestions?
>> >> >> >>>
>> >> >> >>
>> >> >> >
>> >> >> >

Re: P0303 cylinder #3 misfire
 

They are connected with plug wires but they are sealed units and
those connections are not accessible, at least on this setup. Still,
one open plug wire would kill 2 cylinders because of the way the
system operates. For each pair of cylinders, one plug is always fired
negatively, and the other positively. That is, one fires from the
center eletrtode to the outer electrode, and the other fires from the
outer to the center. It's a series circuit. Open a series circuit and
no current flows.



On Sun, 07 Jan 2007 15:01:55 -0500, Mike Romain romainm@sympatico.ca>
wrote:

>What connects the spark plugs to this pack?
>
>Thanks,
>
>Mike
>
>bllsht wrote:
>>
>> One connector, 4 wires. 12v in and 3 driver wires.
>>
>> On Sun, 07 Jan 2007 12:05:11 -0500, Mike Romain <romainm@sympatico.ca>
>> wrote:
>>
>> >Ok, but for one coil power two cylinders I would think there is one
>> >input connection on the coil to rail and one connection going to each
>> >plug with a connection at each plug, no?
>> >
>> >Haven't seen the setup yet.
>> >
>> >Mike
>> >
>> >bllsht wrote:
>> >>
>> >> A bad connection would kill either 2 or all cylinders.
>> >>
>> >> On Sat, 06 Jan 2007 20:32:50 -0500, Mike Romain <romainm@sympatico.ca>
>> >> wrote:
>> >>
>> >> >Or it's electronic plug and socket are dirty.....
>> >> >
>> >> >Mike
>> >> >
>> >> >Jeff Strickland wrote:
>> >> >>
>> >> >> So, one of the coils is bad.
>> >> >>
>> >> >> "Carl" <carlsaiyed@hotmailREMOVE.com> wrote in message
>> >> >> news:bdqdnb4NANz57QHYnZ2dnUVZ_tOmnZ2d@comcast.com. ..
>> >> >> > Jeff, no plug wires or dist cap on an 00 and 01. Coil rail with three coil
>> >> >> > packs.
>> >> >> >
>> >> >> > Carl
>> >> >> >
>> >> >> >
>> >> >> > "Jeff Strickland" <crwlr@yahoo.com> wrote in message
>> >> >> > news:OfidnY5u3NmnmQHYnZ2dnUVZ_h6jnZ2d@ez2.net...
>> >> >> >> With a misfire, I'd be looking at the plug wires or coil. I'd check plug
>> >> >> >> wires if there was a distributor, or I'd look at the coil if there was a
>> >> >> >> separate coil for each cylinder, or a coil for every two cylinders.
>> >> >> >>
>> >> >> >>
>> >> >> >>
>> >> >> >> "01XJ" <adam.tsacoumangos@gmail.com> wrote in message
>> >> >> >> news:1167779855.090317.153570@v33g2000cwv.googlegr oups.com...
>> >> >> >>>I just started experiencing a rough idle on my 2001 Cherokee (78k
>> >> >> >>> miles). My engine light went on a little after that with the P0303
>> >> >> >>> code. I just replaced the spark plugs, but that didn't help anything.
>> >> >> >>> I was
>> >> >> >>> thinking about changing the ignition coil or fuel injector. One other
>> >> >> >>> possibility I was
>> >> >> >>> thinking was checking the cylinder compression (maybe a gasket leak?).
>> >> >> >>> Anyone have any suggestions?
>> >> >> >>>
>> >> >> >>
>> >> >> >
>> >> >> >

Re: P0303 cylinder #3 misfire
 

They are connected with plug wires but they are sealed units and
those connections are not accessible, at least on this setup. Still,
one open plug wire would kill 2 cylinders because of the way the
system operates. For each pair of cylinders, one plug is always fired
negatively, and the other positively. That is, one fires from the
center eletrtode to the outer electrode, and the other fires from the
outer to the center. It's a series circuit. Open a series circuit and
no current flows.



On Sun, 07 Jan 2007 15:01:55 -0500, Mike Romain romainm@sympatico.ca>
wrote:

>What connects the spark plugs to this pack?
>
>Thanks,
>
>Mike
>
>bllsht wrote:
>>
>> One connector, 4 wires. 12v in and 3 driver wires.
>>
>> On Sun, 07 Jan 2007 12:05:11 -0500, Mike Romain <romainm@sympatico.ca>
>> wrote:
>>
>> >Ok, but for one coil power two cylinders I would think there is one
>> >input connection on the coil to rail and one connection going to each
>> >plug with a connection at each plug, no?
>> >
>> >Haven't seen the setup yet.
>> >
>> >Mike
>> >
>> >bllsht wrote:
>> >>
>> >> A bad connection would kill either 2 or all cylinders.
>> >>
>> >> On Sat, 06 Jan 2007 20:32:50 -0500, Mike Romain <romainm@sympatico.ca>
>> >> wrote:
>> >>
>> >> >Or it's electronic plug and socket are dirty.....
>> >> >
>> >> >Mike
>> >> >
>> >> >Jeff Strickland wrote:
>> >> >>
>> >> >> So, one of the coils is bad.
>> >> >>
>> >> >> "Carl" <carlsaiyed@hotmailREMOVE.com> wrote in message
>> >> >> news:bdqdnb4NANz57QHYnZ2dnUVZ_tOmnZ2d@comcast.com. ..
>> >> >> > Jeff, no plug wires or dist cap on an 00 and 01. Coil rail with three coil
>> >> >> > packs.
>> >> >> >
>> >> >> > Carl
>> >> >> >
>> >> >> >
>> >> >> > "Jeff Strickland" <crwlr@yahoo.com> wrote in message
>> >> >> > news:OfidnY5u3NmnmQHYnZ2dnUVZ_h6jnZ2d@ez2.net...
>> >> >> >> With a misfire, I'd be looking at the plug wires or coil. I'd check plug
>> >> >> >> wires if there was a distributor, or I'd look at the coil if there was a
>> >> >> >> separate coil for each cylinder, or a coil for every two cylinders.
>> >> >> >>
>> >> >> >>
>> >> >> >>
>> >> >> >> "01XJ" <adam.tsacoumangos@gmail.com> wrote in message
>> >> >> >> news:1167779855.090317.153570@v33g2000cwv.googlegr oups.com...
>> >> >> >>>I just started experiencing a rough idle on my 2001 Cherokee (78k
>> >> >> >>> miles). My engine light went on a little after that with the P0303
>> >> >> >>> code. I just replaced the spark plugs, but that didn't help anything.
>> >> >> >>> I was
>> >> >> >>> thinking about changing the ignition coil or fuel injector. One other
>> >> >> >>> possibility I was
>> >> >> >>> thinking was checking the cylinder compression (maybe a gasket leak?).
>> >> >> >>> Anyone have any suggestions?
>> >> >> >>>
>> >> >> >>
>> >> >> >
>> >> >> >

Re: P0303 cylinder #3 misfire
 

Thanks, that would eliminate it as his trouble at least.

Mike

bllsht wrote:
>
> They are connected with plug wires but they are sealed units and
> those connections are not accessible, at least on this setup. Still,
> one open plug wire would kill 2 cylinders because of the way the
> system operates. For each pair of cylinders, one plug is always fired
> negatively, and the other positively. That is, one fires from the
> center eletrtode to the outer electrode, and the other fires from the
> outer to the center. It's a series circuit. Open a series circuit and
> no current flows.
>
> On Sun, 07 Jan 2007 15:01:55 -0500, Mike Romain romainm@sympatico.ca>
> wrote:
>
> >What connects the spark plugs to this pack?
> >
> >Thanks,
> >
> >Mike
> >
> >bllsht wrote:
> >>
> >> One connector, 4 wires. 12v in and 3 driver wires.
> >>
> >> On Sun, 07 Jan 2007 12:05:11 -0500, Mike Romain <romainm@sympatico.ca>
> >> wrote:
> >>
> >> >Ok, but for one coil power two cylinders I would think there is one
> >> >input connection on the coil to rail and one connection going to each
> >> >plug with a connection at each plug, no?
> >> >
> >> >Haven't seen the setup yet.
> >> >
> >> >Mike
> >> >
> >> >bllsht wrote:
> >> >>
> >> >> A bad connection would kill either 2 or all cylinders.
> >> >>
> >> >> On Sat, 06 Jan 2007 20:32:50 -0500, Mike Romain <romainm@sympatico.ca>
> >> >> wrote:
> >> >>
> >> >> >Or it's electronic plug and socket are dirty.....
> >> >> >
> >> >> >Mike
> >> >> >
> >> >> >Jeff Strickland wrote:
> >> >> >>
> >> >> >> So, one of the coils is bad.
> >> >> >>
> >> >> >> "Carl" <carlsaiyed@hotmailREMOVE.com> wrote in message
> >> >> >> news:bdqdnb4NANz57QHYnZ2dnUVZ_tOmnZ2d@comcast.com. ..
> >> >> >> > Jeff, no plug wires or dist cap on an 00 and 01. Coil rail with three coil
> >> >> >> > packs.
> >> >> >> >
> >> >> >> > Carl
> >> >> >> >
> >> >> >> >
> >> >> >> > "Jeff Strickland" <crwlr@yahoo.com> wrote in message
> >> >> >> > news:OfidnY5u3NmnmQHYnZ2dnUVZ_h6jnZ2d@ez2.net...
> >> >> >> >> With a misfire, I'd be looking at the plug wires or coil. I'd check plug
> >> >> >> >> wires if there was a distributor, or I'd look at the coil if there was a
> >> >> >> >> separate coil for each cylinder, or a coil for every two cylinders.
> >> >> >> >>
> >> >> >> >>
> >> >> >> >>
> >> >> >> >> "01XJ" <adam.tsacoumangos@gmail.com> wrote in message
> >> >> >> >> news:1167779855.090317.153570@v33g2000cwv.googlegr oups.com...
> >> >> >> >>>I just started experiencing a rough idle on my 2001 Cherokee (78k
> >> >> >> >>> miles). My engine light went on a little after that with the P0303
> >> >> >> >>> code. I just replaced the spark plugs, but that didn't help anything.
> >> >> >> >>> I was
> >> >> >> >>> thinking about changing the ignition coil or fuel injector. One other
> >> >> >> >>> possibility I was
> >> >> >> >>> thinking was checking the cylinder compression (maybe a gasket leak?).
> >> >> >> >>> Anyone have any suggestions?
> >> >> >> >>>
> >> >> >> >>
> >> >> >> >
> >> >> >> >

Re: P0303 cylinder #3 misfire
 

Thanks, that would eliminate it as his trouble at least.

Mike

bllsht wrote:
>
> They are connected with plug wires but they are sealed units and
> those connections are not accessible, at least on this setup. Still,
> one open plug wire would kill 2 cylinders because of the way the
> system operates. For each pair of cylinders, one plug is always fired
> negatively, and the other positively. That is, one fires from the
> center eletrtode to the outer electrode, and the other fires from the
> outer to the center. It's a series circuit. Open a series circuit and
> no current flows.
>
> On Sun, 07 Jan 2007 15:01:55 -0500, Mike Romain romainm@sympatico.ca>
> wrote:
>
> >What connects the spark plugs to this pack?
> >
> >Thanks,
> >
> >Mike
> >
> >bllsht wrote:
> >>
> >> One connector, 4 wires. 12v in and 3 driver wires.
> >>
> >> On Sun, 07 Jan 2007 12:05:11 -0500, Mike Romain <romainm@sympatico.ca>
> >> wrote:
> >>
> >> >Ok, but for one coil power two cylinders I would think there is one
> >> >input connection on the coil to rail and one connection going to each
> >> >plug with a connection at each plug, no?
> >> >
> >> >Haven't seen the setup yet.
> >> >
> >> >Mike
> >> >
> >> >bllsht wrote:
> >> >>
> >> >> A bad connection would kill either 2 or all cylinders.
> >> >>
> >> >> On Sat, 06 Jan 2007 20:32:50 -0500, Mike Romain <romainm@sympatico.ca>
> >> >> wrote:
> >> >>
> >> >> >Or it's electronic plug and socket are dirty.....
> >> >> >
> >> >> >Mike
> >> >> >
> >> >> >Jeff Strickland wrote:
> >> >> >>
> >> >> >> So, one of the coils is bad.
> >> >> >>
> >> >> >> "Carl" <carlsaiyed@hotmailREMOVE.com> wrote in message
> >> >> >> news:bdqdnb4NANz57QHYnZ2dnUVZ_tOmnZ2d@comcast.com. ..
> >> >> >> > Jeff, no plug wires or dist cap on an 00 and 01. Coil rail with three coil
> >> >> >> > packs.
> >> >> >> >
> >> >> >> > Carl
> >> >> >> >
> >> >> >> >
> >> >> >> > "Jeff Strickland" <crwlr@yahoo.com> wrote in message
> >> >> >> > news:OfidnY5u3NmnmQHYnZ2dnUVZ_h6jnZ2d@ez2.net...
> >> >> >> >> With a misfire, I'd be looking at the plug wires or coil. I'd check plug
> >> >> >> >> wires if there was a distributor, or I'd look at the coil if there was a
> >> >> >> >> separate coil for each cylinder, or a coil for every two cylinders.
> >> >> >> >>
> >> >> >> >>
> >> >> >> >>
> >> >> >> >> "01XJ" <adam.tsacoumangos@gmail.com> wrote in message
> >> >> >> >> news:1167779855.090317.153570@v33g2000cwv.googlegr oups.com...
> >> >> >> >>>I just started experiencing a rough idle on my 2001 Cherokee (78k
> >> >> >> >>> miles). My engine light went on a little after that with the P0303
> >> >> >> >>> code. I just replaced the spark plugs, but that didn't help anything.
> >> >> >> >>> I was
> >> >> >> >>> thinking about changing the ignition coil or fuel injector. One other
> >> >> >> >>> possibility I was
> >> >> >> >>> thinking was checking the cylinder compression (maybe a gasket leak?).
> >> >> >> >>> Anyone have any suggestions?
> >> >> >> >>>
> >> >> >> >>
> >> >> >> >
> >> >> >> >

Re: P0303 cylinder #3 misfire
 

Thanks, that would eliminate it as his trouble at least.

Mike

bllsht wrote:
>
> They are connected with plug wires but they are sealed units and
> those connections are not accessible, at least on this setup. Still,
> one open plug wire would kill 2 cylinders because of the way the
> system operates. For each pair of cylinders, one plug is always fired
> negatively, and the other positively. That is, one fires from the
> center eletrtode to the outer electrode, and the other fires from the
> outer to the center. It's a series circuit. Open a series circuit and
> no current flows.
>
> On Sun, 07 Jan 2007 15:01:55 -0500, Mike Romain romainm@sympatico.ca>
> wrote:
>
> >What connects the spark plugs to this pack?
> >
> >Thanks,
> >
> >Mike
> >
> >bllsht wrote:
> >>
> >> One connector, 4 wires. 12v in and 3 driver wires.
> >>
> >> On Sun, 07 Jan 2007 12:05:11 -0500, Mike Romain <romainm@sympatico.ca>
> >> wrote:
> >>
> >> >Ok, but for one coil power two cylinders I would think there is one
> >> >input connection on the coil to rail and one connection going to each
> >> >plug with a connection at each plug, no?
> >> >
> >> >Haven't seen the setup yet.
> >> >
> >> >Mike
> >> >
> >> >bllsht wrote:
> >> >>
> >> >> A bad connection would kill either 2 or all cylinders.
> >> >>
> >> >> On Sat, 06 Jan 2007 20:32:50 -0500, Mike Romain <romainm@sympatico.ca>
> >> >> wrote:
> >> >>
> >> >> >Or it's electronic plug and socket are dirty.....
> >> >> >
> >> >> >Mike
> >> >> >
> >> >> >Jeff Strickland wrote:
> >> >> >>
> >> >> >> So, one of the coils is bad.
> >> >> >>
> >> >> >> "Carl" <carlsaiyed@hotmailREMOVE.com> wrote in message
> >> >> >> news:bdqdnb4NANz57QHYnZ2dnUVZ_tOmnZ2d@comcast.com. ..
> >> >> >> > Jeff, no plug wires or dist cap on an 00 and 01. Coil rail with three coil
> >> >> >> > packs.
> >> >> >> >
> >> >> >> > Carl
> >> >> >> >
> >> >> >> >
> >> >> >> > "Jeff Strickland" <crwlr@yahoo.com> wrote in message
> >> >> >> > news:OfidnY5u3NmnmQHYnZ2dnUVZ_h6jnZ2d@ez2.net...
> >> >> >> >> With a misfire, I'd be looking at the plug wires or coil. I'd check plug
> >> >> >> >> wires if there was a distributor, or I'd look at the coil if there was a
> >> >> >> >> separate coil for each cylinder, or a coil for every two cylinders.
> >> >> >> >>
> >> >> >> >>
> >> >> >> >>
> >> >> >> >> "01XJ" <adam.tsacoumangos@gmail.com> wrote in message
> >> >> >> >> news:1167779855.090317.153570@v33g2000cwv.googlegr oups.com...
> >> >> >> >>>I just started experiencing a rough idle on my 2001 Cherokee (78k
> >> >> >> >>> miles). My engine light went on a little after that with the P0303
> >> >> >> >>> code. I just replaced the spark plugs, but that didn't help anything.
> >> >> >> >>> I was
> >> >> >> >>> thinking about changing the ignition coil or fuel injector. One other
> >> >> >> >>> possibility I was
> >> >> >> >>> thinking was checking the cylinder compression (maybe a gasket leak?).
> >> >> >> >>> Anyone have any suggestions?
> >> >> >> >>>
> >> >> >> >>
> >> >> >> >
> >> >> >> >

Re: P0303 cylinder #3 misfire
 

Just out of curiosity, what's your source for this? I know the packs fire
two sets of plugs but I wasn't aware it fired pos/neg, and there's no
mention of it in the FSM that I can find.

"bllsht" <nospam@dot.net> wrote in message
news:t1t2q2daj61omiaa6ammb7br9fs4k1te9r@4ax.com...
.. For each pair of cylinders, one plug is always fired
> negatively, and the other positively. That is, one fires from the
> center eletrtode to the outer electrode, and the other fires from the
> outer to the center. It's a series circuit. Open a series circuit and
> no current flows.
>
>
>

Re: P0303 cylinder #3 misfire
 

Just out of curiosity, what's your source for this? I know the packs fire
two sets of plugs but I wasn't aware it fired pos/neg, and there's no
mention of it in the FSM that I can find.

"bllsht" <nospam@dot.net> wrote in message
news:t1t2q2daj61omiaa6ammb7br9fs4k1te9r@4ax.com...
.. For each pair of cylinders, one plug is always fired
> negatively, and the other positively. That is, one fires from the
> center eletrtode to the outer electrode, and the other fires from the
> outer to the center. It's a series circuit. Open a series circuit and
> no current flows.
>
>
>

Re: P0303 cylinder #3 misfire
 

Just out of curiosity, what's your source for this? I know the packs fire
two sets of plugs but I wasn't aware it fired pos/neg, and there's no
mention of it in the FSM that I can find.

"bllsht" <nospam@dot.net> wrote in message
news:t1t2q2daj61omiaa6ammb7br9fs4k1te9r@4ax.com...
.. For each pair of cylinders, one plug is always fired
> negatively, and the other positively. That is, one fires from the
> center eletrtode to the outer electrode, and the other fires from the
> outer to the center. It's a series circuit. Open a series circuit and
> no current flows.
>
>
>

Re: P0303 cylinder #3 misfire
 

The FSM is a good source for repair info, but it doesn't go into all
of the details.

The 4.0L uses a waste spark system. That is it uses one coil to fire a
pair of spark plugs simultaneously. One on the compression stroke and
the other being wasted on the exhaust stroke. One post of the coil
fires with positive potential and the other negative.

A picture will make it easier. Scroll down to the DIS section for an
illustration of what goes on.

http://www.motorage.com/motorage/art....jsp?id=140913


On Sun, 7 Jan 2007 22:28:31 -0500, "Matt Macchiarolo"
<matt@nospamplease.com> wrote:

>Just out of curiosity, what's your source for this? I know the packs fire
>two sets of plugs but I wasn't aware it fired pos/neg, and there's no
>mention of it in the FSM that I can find.
>
>"bllsht" <nospam@dot.net> wrote in message
>news:t1t2q2daj61omiaa6ammb7br9fs4k1te9r@4ax.com.. .
>. For each pair of cylinders, one plug is always fired
>> negatively, and the other positively. That is, one fires from the
>> center eletrtode to the outer electrode, and the other fires from the
>> outer to the center. It's a series circuit. Open a series circuit and
>> no current flows.
>>
>>
>>
>

Re: P0303 cylinder #3 misfire
 

The FSM is a good source for repair info, but it doesn't go into all
of the details.

The 4.0L uses a waste spark system. That is it uses one coil to fire a
pair of spark plugs simultaneously. One on the compression stroke and
the other being wasted on the exhaust stroke. One post of the coil
fires with positive potential and the other negative.

A picture will make it easier. Scroll down to the DIS section for an
illustration of what goes on.

http://www.motorage.com/motorage/art....jsp?id=140913


On Sun, 7 Jan 2007 22:28:31 -0500, "Matt Macchiarolo"
<matt@nospamplease.com> wrote:

>Just out of curiosity, what's your source for this? I know the packs fire
>two sets of plugs but I wasn't aware it fired pos/neg, and there's no
>mention of it in the FSM that I can find.
>
>"bllsht" <nospam@dot.net> wrote in message
>news:t1t2q2daj61omiaa6ammb7br9fs4k1te9r@4ax.com.. .
>. For each pair of cylinders, one plug is always fired
>> negatively, and the other positively. That is, one fires from the
>> center eletrtode to the outer electrode, and the other fires from the
>> outer to the center. It's a series circuit. Open a series circuit and
>> no current flows.
>>
>>
>>
>

Re: P0303 cylinder #3 misfire
 

The FSM is a good source for repair info, but it doesn't go into all
of the details.

The 4.0L uses a waste spark system. That is it uses one coil to fire a
pair of spark plugs simultaneously. One on the compression stroke and
the other being wasted on the exhaust stroke. One post of the coil
fires with positive potential and the other negative.

A picture will make it easier. Scroll down to the DIS section for an
illustration of what goes on.

http://www.motorage.com/motorage/art....jsp?id=140913


On Sun, 7 Jan 2007 22:28:31 -0500, "Matt Macchiarolo"
<matt@nospamplease.com> wrote:

>Just out of curiosity, what's your source for this? I know the packs fire
>two sets of plugs but I wasn't aware it fired pos/neg, and there's no
>mention of it in the FSM that I can find.
>
>"bllsht" <nospam@dot.net> wrote in message
>news:t1t2q2daj61omiaa6ammb7br9fs4k1te9r@4ax.com.. .
>. For each pair of cylinders, one plug is always fired
>> negatively, and the other positively. That is, one fires from the
>> center eletrtode to the outer electrode, and the other fires from the
>> outer to the center. It's a series circuit. Open a series circuit and
>> no current flows.
>>
>>
>>
>

Re: P0303 cylinder #3 misfire
 

Hmm, neat. Thanks!

"bllsht" <nospam@dot.net> wrote in message
news:6fi3q2pautrue37o9cssrja8cuf5vvc8b8@4ax.com...
> The FSM is a good source for repair info, but it doesn't go into all
> of the details.
>
> The 4.0L uses a waste spark system. That is it uses one coil to fire a
> pair of spark plugs simultaneously. One on the compression stroke and
> the other being wasted on the exhaust stroke. One post of the coil
> fires with positive potential and the other negative.
>
> A picture will make it easier. Scroll down to the DIS section for an
> illustration of what goes on.
>
> http://www.motorage.com/motorage/art....jsp?id=140913
>
>
> On Sun, 7 Jan 2007 22:28:31 -0500, "Matt Macchiarolo"
> <matt@nospamplease.com> wrote:
>
>>Just out of curiosity, what's your source for this? I know the packs fire
>>two sets of plugs but I wasn't aware it fired pos/neg, and there's no
>>mention of it in the FSM that I can find.
>>
>>"bllsht" <nospam@dot.net> wrote in message
>>news:t1t2q2daj61omiaa6ammb7br9fs4k1te9r@4ax.com. ..
>>. For each pair of cylinders, one plug is always fired
>>> negatively, and the other positively. That is, one fires from the
>>> center eletrtode to the outer electrode, and the other fires from the
>>> outer to the center. It's a series circuit. Open a series circuit and
>>> no current flows.
>>>
>>>
>>>
>>

Re: P0303 cylinder #3 misfire
 

Hmm, neat. Thanks!

"bllsht" <nospam@dot.net> wrote in message
news:6fi3q2pautrue37o9cssrja8cuf5vvc8b8@4ax.com...
> The FSM is a good source for repair info, but it doesn't go into all
> of the details.
>
> The 4.0L uses a waste spark system. That is it uses one coil to fire a
> pair of spark plugs simultaneously. One on the compression stroke and
> the other being wasted on the exhaust stroke. One post of the coil
> fires with positive potential and the other negative.
>
> A picture will make it easier. Scroll down to the DIS section for an
> illustration of what goes on.
>
> http://www.motorage.com/motorage/art....jsp?id=140913
>
>
> On Sun, 7 Jan 2007 22:28:31 -0500, "Matt Macchiarolo"
> <matt@nospamplease.com> wrote:
>
>>Just out of curiosity, what's your source for this? I know the packs fire
>>two sets of plugs but I wasn't aware it fired pos/neg, and there's no
>>mention of it in the FSM that I can find.
>>
>>"bllsht" <nospam@dot.net> wrote in message
>>news:t1t2q2daj61omiaa6ammb7br9fs4k1te9r@4ax.com. ..
>>. For each pair of cylinders, one plug is always fired
>>> negatively, and the other positively. That is, one fires from the
>>> center eletrtode to the outer electrode, and the other fires from the
>>> outer to the center. It's a series circuit. Open a series circuit and
>>> no current flows.
>>>
>>>
>>>
>>

Re: P0303 cylinder #3 misfire
 

Hmm, neat. Thanks!

"bllsht" <nospam@dot.net> wrote in message
news:6fi3q2pautrue37o9cssrja8cuf5vvc8b8@4ax.com...
> The FSM is a good source for repair info, but it doesn't go into all
> of the details.
>
> The 4.0L uses a waste spark system. That is it uses one coil to fire a
> pair of spark plugs simultaneously. One on the compression stroke and
> the other being wasted on the exhaust stroke. One post of the coil
> fires with positive potential and the other negative.
>
> A picture will make it easier. Scroll down to the DIS section for an
> illustration of what goes on.
>
> http://www.motorage.com/motorage/art....jsp?id=140913
>
>
> On Sun, 7 Jan 2007 22:28:31 -0500, "Matt Macchiarolo"
> <matt@nospamplease.com> wrote:
>
>>Just out of curiosity, what's your source for this? I know the packs fire
>>two sets of plugs but I wasn't aware it fired pos/neg, and there's no
>>mention of it in the FSM that I can find.
>>
>>"bllsht" <nospam@dot.net> wrote in message
>>news:t1t2q2daj61omiaa6ammb7br9fs4k1te9r@4ax.com. ..
>>. For each pair of cylinders, one plug is always fired
>>> negatively, and the other positively. That is, one fires from the
>>> center eletrtode to the outer electrode, and the other fires from the
>>> outer to the center. It's a series circuit. Open a series circuit and
>>> no current flows.
>>>
>>>
>>>
>>

Re: P0303 cylinder #3 misfire
 

Hi all, here is an update on my 2001 TJ from a previous reply in this
thread. After replacing the broken bridge and reassembling the rocker, a
test drive showed some improvement but the Jeep threw the P0302 engine code
again. After several days of digging into possibilities and a few calls to
Chrysler, the guys finally dug out the problem. The cam had a bad lobe on
one of the number two valves. I now have a pretty much rebuilt top end, new
lifters, cam, rockers, timing chain and gears, etc.. They showed me the old
cam and, while the Chrysler tech wouldn't admit a bad heat treat to begin
with, he did say that he has seen a "few" but they are not common to have go
bad. The TJ came home today, runs great, nice and quiet, smooth at idle and
driving speeds. I'm just over $700 lighter in the wallet but I should be
able to run this engine til I decide I need a newer Jeep. Just wanted to
let the group know the update on my problem about my misfire.
Les

"01XJ" <adam.tsacoumangos@gmail.com> wrote in message
news:1167779855.090317.153570@v33g2000cwv.googlegr oups.com...
>I just started experiencing a rough idle on my 2001 Cherokee (78k
> miles). My engine light went on a little after that with the P0303
> code. I just replaced the spark plugs, but that didn't help anything.
> I was
> thinking about changing the ignition coil or fuel injector. One other
> possibility I was
> thinking was checking the cylinder compression (maybe a gasket leak?).
> Anyone have any suggestions?
>

Re: P0303 cylinder #3 misfire
 

Hi all, here is an update on my 2001 TJ from a previous reply in this
thread. After replacing the broken bridge and reassembling the rocker, a
test drive showed some improvement but the Jeep threw the P0302 engine code
again. After several days of digging into possibilities and a few calls to
Chrysler, the guys finally dug out the problem. The cam had a bad lobe on
one of the number two valves. I now have a pretty much rebuilt top end, new
lifters, cam, rockers, timing chain and gears, etc.. They showed me the old
cam and, while the Chrysler tech wouldn't admit a bad heat treat to begin
with, he did say that he has seen a "few" but they are not common to have go
bad. The TJ came home today, runs great, nice and quiet, smooth at idle and
driving speeds. I'm just over $700 lighter in the wallet but I should be
able to run this engine til I decide I need a newer Jeep. Just wanted to
let the group know the update on my problem about my misfire.
Les

"01XJ" <adam.tsacoumangos@gmail.com> wrote in message
news:1167779855.090317.153570@v33g2000cwv.googlegr oups.com...
>I just started experiencing a rough idle on my 2001 Cherokee (78k
> miles). My engine light went on a little after that with the P0303
> code. I just replaced the spark plugs, but that didn't help anything.
> I was
> thinking about changing the ignition coil or fuel injector. One other
> possibility I was
> thinking was checking the cylinder compression (maybe a gasket leak?).
> Anyone have any suggestions?
>

Re: P0303 cylinder #3 misfire
 

Hi all, here is an update on my 2001 TJ from a previous reply in this
thread. After replacing the broken bridge and reassembling the rocker, a
test drive showed some improvement but the Jeep threw the P0302 engine code
again. After several days of digging into possibilities and a few calls to
Chrysler, the guys finally dug out the problem. The cam had a bad lobe on
one of the number two valves. I now have a pretty much rebuilt top end, new
lifters, cam, rockers, timing chain and gears, etc.. They showed me the old
cam and, while the Chrysler tech wouldn't admit a bad heat treat to begin
with, he did say that he has seen a "few" but they are not common to have go
bad. The TJ came home today, runs great, nice and quiet, smooth at idle and
driving speeds. I'm just over $700 lighter in the wallet but I should be
able to run this engine til I decide I need a newer Jeep. Just wanted to
let the group know the update on my problem about my misfire.
Les

"01XJ" <adam.tsacoumangos@gmail.com> wrote in message
news:1167779855.090317.153570@v33g2000cwv.googlegr oups.com...
>I just started experiencing a rough idle on my 2001 Cherokee (78k
> miles). My engine light went on a little after that with the P0303
> code. I just replaced the spark plugs, but that didn't help anything.
> I was
> thinking about changing the ignition coil or fuel injector. One other
> possibility I was
> thinking was checking the cylinder compression (maybe a gasket leak?).
> Anyone have any suggestions?
>

Re: P0303 cylinder #3 misfire
 

Les,

Thanks for the follow up.

Carl


"Les" <wiedrick@twcny.rr.com> wrote in message
news:45a45c4e$0$8920$4c368faf@roadrunner.com...
> Hi all, here is an update on my 2001 TJ from a previous reply in this
> thread. After replacing the broken bridge and reassembling the rocker, a
> test drive showed some improvement but the Jeep threw the P0302 engine
> code again. After several days of digging into possibilities and a few
> calls to Chrysler, the guys finally dug out the problem. The cam had a bad
> lobe on one of the number two valves. I now have a pretty much rebuilt top
> end, new lifters, cam, rockers, timing chain and gears, etc.. They showed
> me the old cam and, while the Chrysler tech wouldn't admit a bad heat
> treat to begin with, he did say that he has seen a "few" but they are not
> common to have go bad. The TJ came home today, runs great, nice and
> quiet, smooth at idle and driving speeds. I'm just over $700 lighter in
> the wallet but I should be able to run this engine til I decide I need a
> newer Jeep. Just wanted to let the group know the update on my problem
> about my misfire.
> Les
>
> "01XJ" <adam.tsacoumangos@gmail.com> wrote in message
> news:1167779855.090317.153570@v33g2000cwv.googlegr oups.com...
>>I just started experiencing a rough idle on my 2001 Cherokee (78k
>> miles). My engine light went on a little after that with the P0303
>> code. I just replaced the spark plugs, but that didn't help anything.
>> I was
>> thinking about changing the ignition coil or fuel injector. One other
>> possibility I was
>> thinking was checking the cylinder compression (maybe a gasket leak?).
>> Anyone have any suggestions?
>>
>
>

Re: P0303 cylinder #3 misfire
 

Les,

Thanks for the follow up.

Carl


"Les" <wiedrick@twcny.rr.com> wrote in message
news:45a45c4e$0$8920$4c368faf@roadrunner.com...
> Hi all, here is an update on my 2001 TJ from a previous reply in this
> thread. After replacing the broken bridge and reassembling the rocker, a
> test drive showed some improvement but the Jeep threw the P0302 engine
> code again. After several days of digging into possibilities and a few
> calls to Chrysler, the guys finally dug out the problem. The cam had a bad
> lobe on one of the number two valves. I now have a pretty much rebuilt top
> end, new lifters, cam, rockers, timing chain and gears, etc.. They showed
> me the old cam and, while the Chrysler tech wouldn't admit a bad heat
> treat to begin with, he did say that he has seen a "few" but they are not
> common to have go bad. The TJ came home today, runs great, nice and
> quiet, smooth at idle and driving speeds. I'm just over $700 lighter in
> the wallet but I should be able to run this engine til I decide I need a
> newer Jeep. Just wanted to let the group know the update on my problem
> about my misfire.
> Les
>
> "01XJ" <adam.tsacoumangos@gmail.com> wrote in message
> news:1167779855.090317.153570@v33g2000cwv.googlegr oups.com...
>>I just started experiencing a rough idle on my 2001 Cherokee (78k
>> miles). My engine light went on a little after that with the P0303
>> code. I just replaced the spark plugs, but that didn't help anything.
>> I was
>> thinking about changing the ignition coil or fuel injector. One other
>> possibility I was
>> thinking was checking the cylinder compression (maybe a gasket leak?).
>> Anyone have any suggestions?
>>
>
>

Re: P0303 cylinder #3 misfire
 

Les,

Thanks for the follow up.

Carl


"Les" <wiedrick@twcny.rr.com> wrote in message
news:45a45c4e$0$8920$4c368faf@roadrunner.com...
> Hi all, here is an update on my 2001 TJ from a previous reply in this
> thread. After replacing the broken bridge and reassembling the rocker, a
> test drive showed some improvement but the Jeep threw the P0302 engine
> code again. After several days of digging into possibilities and a few
> calls to Chrysler, the guys finally dug out the problem. The cam had a bad
> lobe on one of the number two valves. I now have a pretty much rebuilt top
> end, new lifters, cam, rockers, timing chain and gears, etc.. They showed
> me the old cam and, while the Chrysler tech wouldn't admit a bad heat
> treat to begin with, he did say that he has seen a "few" but they are not
> common to have go bad. The TJ came home today, runs great, nice and
> quiet, smooth at idle and driving speeds. I'm just over $700 lighter in
> the wallet but I should be able to run this engine til I decide I need a
> newer Jeep. Just wanted to let the group know the update on my problem
> about my misfire.
> Les
>
> "01XJ" <adam.tsacoumangos@gmail.com> wrote in message
> news:1167779855.090317.153570@v33g2000cwv.googlegr oups.com...
>>I just started experiencing a rough idle on my 2001 Cherokee (78k
>> miles). My engine light went on a little after that with the P0303
>> code. I just replaced the spark plugs, but that didn't help anything.
>> I was
>> thinking about changing the ignition coil or fuel injector. One other
>> possibility I was
>> thinking was checking the cylinder compression (maybe a gasket leak?).
>> Anyone have any suggestions?
>>
>
>

Re: P0303 cylinder #3 misfire
 

I just talked to the dealer who said the heat shield had been put on
the intake to prevent overheating injector #3. I guess it rules that
one out. I'll try looking at the injector this weekend. I'll wait on
checking the coil since it would most likely affect 2 cylinders,
although I'll keep it in the back of my head to not rule it out
completely.

Thanks everyone.

On Jan 9, 10:07 pm, "Carl" <carlsai...@hotmailREMOVE.com> wrote:
> Les,
>
> Thanks for the follow up.
>
> Carl
>
> "Les" <wiedr...@twcny.rr.com> wrote in messagenews:45a45c4e$0$8920$4c368faf@roadrunner.co m...
>
> > Hi all, here is an update on my 2001 TJ from a previous reply in this
> > thread. After replacing the broken bridge and reassembling the rocker, a
> > test drive showed some improvement but the Jeep threw the P0302 engine
> > code again. After several days of digging into possibilities and a few
> > calls to Chrysler, the guys finally dug out the problem. The cam had a bad
> > lobe on one of the number two valves. I now have a pretty much rebuilt top
> > end, new lifters, cam, rockers, timing chain and gears, etc.. They showed
> > me the old cam and, while the Chrysler tech wouldn't admit a bad heat
> > treat to begin with, he did say that he has seen a "few" but they are not
> > common to have go bad. The TJ came home today, runs great, nice and
> > quiet, smooth at idle and driving speeds. I'm just over $700 lighter in
> > the wallet but I should be able to run this engine til I decide I need a
> > newer Jeep. Just wanted to let the group know the update on my problem
> > about my misfire.
> > Les
>
> > "01XJ" <adam.tsacouman...@gmail.com> wrote in message
> >news:1167779855.090317.153570@v33g2000cwv.googleg roups.com...
> >>I just started experiencing a rough idle on my 2001 Cherokee (78k
> >> miles). My engine light went on a little after that with the P0303
> >> code. I just replaced the spark plugs, but that didn't help anything.
> >> I was
> >> thinking about changing the ignition coil or fuel injector. One other
> >> possibility I was
> >> thinking was checking the cylinder compression (maybe a gasket leak?).
> >> Anyone have any suggestions?