CJ5 misfires at high RPM/hard acceleration
 

Gentlemen,

I'm having some problems tracking this down. When I accelerate hard
or get up to a certain RPM (about 3000) at cruising, I get popping
coming out of my exhaust & a huge lack in power. The engine has never
stalled, but I can't go any faster in that gear due to the misfiring.
I've done almost everything that I can think of short of checking the
timing chain & replacing the carburetor. Here's what I've done so
far:

Changed coil + ballast resistor + ignition wires/wire to distributor
Changed fuel filter + replaced all fuel lines
Changed fuel pump
Changed points + condenser
Changed plugs + plug wires (plugs gapped at .035)
Changed cap + rotor
Changed vacuum advance (this was confirmed bad & made a huge
difference)

The initial timing is 6 degrees BTDC & the dwell angle is about 31. I
get about 16hg of steady vacuum at idle & about 7psi of fuel pressure
at idle. The idle & even light acceleration is perfect, which makes
me think it's not a timing chain issue, but I don't know enough about
what the symptoms of a slipped chain would be to make that call. When
the engine is at TDC of piston 1's compression stroke, the rotor lines
up perfectly with cylinder 1's plug wire, which also makes me thing
it's not necessarily a timing chain issue. Since I have changed the
plugs & tried to further diagnose the problem, my plugs have turned
black. This along with the popping in the exhaust obviously mean my
mixture is either too rich, or something is going haywire with the
timing & causing the fuel to not burn at higher RPM. One thing worth
noting, is that I have not changed the plugs since they have been
fouled since I replaced the faulty vacuum advance. I didn't know if
this would make a difference or not & didn't want to risk fouling a
new set while troubleshooting. I can literally get flames to shoot
out of my exhaust if I abuse it enough. This happens on both sides &
I have dual exhaust, leading me to think it's not a valve issue,
unless I'm really unlucky & have a problem on both sides of the
engine.

The jeep is a recreational vehicle of sorts, used primarily to climb
up & down sand dunes. The symptoms all occured when my fuel pump died
about 2 years ago. After I replaced the pump, the engine started
doing this. I've since replaced it again to rule that out with no
change. I've also rebuilt the carburetor, but it was the first time I
ever did such a thing, so it's quite possible I missed something. The
accelerator pump works fine, the idle mixture screws are set very lean
(since I think the mixture is too rich for some reason), the power
valve has been replaced & I even checked it again last week & I can
see spray coming out of the booster venturi when I rev the engine (it
does this whether I'm moving or not). Another thing I noticed is that
when the engine is cold, if I hold my hand in front of the exhaust, it
sprays black fluid on me at idle. It's not a lot, but I noticed it
when it was sprayed on my leg one day. It has no smell to it other
than stinky exhaust, so I don't really know what this is. My coolant
level has not changed noticeably, so I wouldn't think it to be a water
leak, but I can't say with certainty.

Here are the basics:
1972 Jeep CJ5
AMC 304
Aftermarket parts:
Edlebrock peformer intake
Holley 600cfm 4-bbl carb
Edlebrock shorty headers

Thanks for any help you guys can give on this. I'm at a loss & don't
know what to do next.

-Matt

Re: CJ5 misfires at high RPM/hard acceleration
 

If the plugs are just fouled, I would pull them out and clean them up with
some light brushing and some B-12chemtool. Re-gap, re-install, and see if
that helps.

Carl


<matthew.nye@gmail.com> wrote in message
news:1184524973.150369.268860@22g2000hsm.googlegro ups.com...
> Gentlemen,
>
> I'm having some problems tracking this down. When I accelerate hard
> or get up to a certain RPM (about 3000) at cruising, I get popping
> coming out of my exhaust & a huge lack in power. The engine has never
> stalled, but I can't go any faster in that gear due to the misfiring.
> I've done almost everything that I can think of short of checking the
> timing chain & replacing the carburetor. Here's what I've done so
> far:
>
> Changed coil + ballast resistor + ignition wires/wire to distributor
> Changed fuel filter + replaced all fuel lines
> Changed fuel pump
> Changed points + condenser
> Changed plugs + plug wires (plugs gapped at .035)
> Changed cap + rotor
> Changed vacuum advance (this was confirmed bad & made a huge
> difference)
>
> The initial timing is 6 degrees BTDC & the dwell angle is about 31. I
> get about 16hg of steady vacuum at idle & about 7psi of fuel pressure
> at idle. The idle & even light acceleration is perfect, which makes
> me think it's not a timing chain issue, but I don't know enough about
> what the symptoms of a slipped chain would be to make that call. When
> the engine is at TDC of piston 1's compression stroke, the rotor lines
> up perfectly with cylinder 1's plug wire, which also makes me thing
> it's not necessarily a timing chain issue. Since I have changed the
> plugs & tried to further diagnose the problem, my plugs have turned
> black. This along with the popping in the exhaust obviously mean my
> mixture is either too rich, or something is going haywire with the
> timing & causing the fuel to not burn at higher RPM. One thing worth
> noting, is that I have not changed the plugs since they have been
> fouled since I replaced the faulty vacuum advance. I didn't know if
> this would make a difference or not & didn't want to risk fouling a
> new set while troubleshooting. I can literally get flames to shoot
> out of my exhaust if I abuse it enough. This happens on both sides &
> I have dual exhaust, leading me to think it's not a valve issue,
> unless I'm really unlucky & have a problem on both sides of the
> engine.
>
> The jeep is a recreational vehicle of sorts, used primarily to climb
> up & down sand dunes. The symptoms all occured when my fuel pump died
> about 2 years ago. After I replaced the pump, the engine started
> doing this. I've since replaced it again to rule that out with no
> change. I've also rebuilt the carburetor, but it was the first time I
> ever did such a thing, so it's quite possible I missed something. The
> accelerator pump works fine, the idle mixture screws are set very lean
> (since I think the mixture is too rich for some reason), the power
> valve has been replaced & I even checked it again last week & I can
> see spray coming out of the booster venturi when I rev the engine (it
> does this whether I'm moving or not). Another thing I noticed is that
> when the engine is cold, if I hold my hand in front of the exhaust, it
> sprays black fluid on me at idle. It's not a lot, but I noticed it
> when it was sprayed on my leg one day. It has no smell to it other
> than stinky exhaust, so I don't really know what this is. My coolant
> level has not changed noticeably, so I wouldn't think it to be a water
> leak, but I can't say with certainty.
>
> Here are the basics:
> 1972 Jeep CJ5
> AMC 304
> Aftermarket parts:
> Edlebrock peformer intake
> Holley 600cfm 4-bbl carb
> Edlebrock shorty headers
>
> Thanks for any help you guys can give on this. I'm at a loss & don't
> know what to do next.
>
> -Matt
>

Re: CJ5 misfires at high RPM/hard acceleration
 

If the plugs are just fouled, I would pull them out and clean them up with
some light brushing and some B-12chemtool. Re-gap, re-install, and see if
that helps.

Carl


<matthew.nye@gmail.com> wrote in message
news:1184524973.150369.268860@22g2000hsm.googlegro ups.com...
> Gentlemen,
>
> I'm having some problems tracking this down. When I accelerate hard
> or get up to a certain RPM (about 3000) at cruising, I get popping
> coming out of my exhaust & a huge lack in power. The engine has never
> stalled, but I can't go any faster in that gear due to the misfiring.
> I've done almost everything that I can think of short of checking the
> timing chain & replacing the carburetor. Here's what I've done so
> far:
>
> Changed coil + ballast resistor + ignition wires/wire to distributor
> Changed fuel filter + replaced all fuel lines
> Changed fuel pump
> Changed points + condenser
> Changed plugs + plug wires (plugs gapped at .035)
> Changed cap + rotor
> Changed vacuum advance (this was confirmed bad & made a huge
> difference)
>
> The initial timing is 6 degrees BTDC & the dwell angle is about 31. I
> get about 16hg of steady vacuum at idle & about 7psi of fuel pressure
> at idle. The idle & even light acceleration is perfect, which makes
> me think it's not a timing chain issue, but I don't know enough about
> what the symptoms of a slipped chain would be to make that call. When
> the engine is at TDC of piston 1's compression stroke, the rotor lines
> up perfectly with cylinder 1's plug wire, which also makes me thing
> it's not necessarily a timing chain issue. Since I have changed the
> plugs & tried to further diagnose the problem, my plugs have turned
> black. This along with the popping in the exhaust obviously mean my
> mixture is either too rich, or something is going haywire with the
> timing & causing the fuel to not burn at higher RPM. One thing worth
> noting, is that I have not changed the plugs since they have been
> fouled since I replaced the faulty vacuum advance. I didn't know if
> this would make a difference or not & didn't want to risk fouling a
> new set while troubleshooting. I can literally get flames to shoot
> out of my exhaust if I abuse it enough. This happens on both sides &
> I have dual exhaust, leading me to think it's not a valve issue,
> unless I'm really unlucky & have a problem on both sides of the
> engine.
>
> The jeep is a recreational vehicle of sorts, used primarily to climb
> up & down sand dunes. The symptoms all occured when my fuel pump died
> about 2 years ago. After I replaced the pump, the engine started
> doing this. I've since replaced it again to rule that out with no
> change. I've also rebuilt the carburetor, but it was the first time I
> ever did such a thing, so it's quite possible I missed something. The
> accelerator pump works fine, the idle mixture screws are set very lean
> (since I think the mixture is too rich for some reason), the power
> valve has been replaced & I even checked it again last week & I can
> see spray coming out of the booster venturi when I rev the engine (it
> does this whether I'm moving or not). Another thing I noticed is that
> when the engine is cold, if I hold my hand in front of the exhaust, it
> sprays black fluid on me at idle. It's not a lot, but I noticed it
> when it was sprayed on my leg one day. It has no smell to it other
> than stinky exhaust, so I don't really know what this is. My coolant
> level has not changed noticeably, so I wouldn't think it to be a water
> leak, but I can't say with certainty.
>
> Here are the basics:
> 1972 Jeep CJ5
> AMC 304
> Aftermarket parts:
> Edlebrock peformer intake
> Holley 600cfm 4-bbl carb
> Edlebrock shorty headers
>
> Thanks for any help you guys can give on this. I'm at a loss & don't
> know what to do next.
>
> -Matt
>

Re: CJ5 misfires at high RPM/hard acceleration
 

If the plugs are just fouled, I would pull them out and clean them up with
some light brushing and some B-12chemtool. Re-gap, re-install, and see if
that helps.

Carl


<matthew.nye@gmail.com> wrote in message
news:1184524973.150369.268860@22g2000hsm.googlegro ups.com...
> Gentlemen,
>
> I'm having some problems tracking this down. When I accelerate hard
> or get up to a certain RPM (about 3000) at cruising, I get popping
> coming out of my exhaust & a huge lack in power. The engine has never
> stalled, but I can't go any faster in that gear due to the misfiring.
> I've done almost everything that I can think of short of checking the
> timing chain & replacing the carburetor. Here's what I've done so
> far:
>
> Changed coil + ballast resistor + ignition wires/wire to distributor
> Changed fuel filter + replaced all fuel lines
> Changed fuel pump
> Changed points + condenser
> Changed plugs + plug wires (plugs gapped at .035)
> Changed cap + rotor
> Changed vacuum advance (this was confirmed bad & made a huge
> difference)
>
> The initial timing is 6 degrees BTDC & the dwell angle is about 31. I
> get about 16hg of steady vacuum at idle & about 7psi of fuel pressure
> at idle. The idle & even light acceleration is perfect, which makes
> me think it's not a timing chain issue, but I don't know enough about
> what the symptoms of a slipped chain would be to make that call. When
> the engine is at TDC of piston 1's compression stroke, the rotor lines
> up perfectly with cylinder 1's plug wire, which also makes me thing
> it's not necessarily a timing chain issue. Since I have changed the
> plugs & tried to further diagnose the problem, my plugs have turned
> black. This along with the popping in the exhaust obviously mean my
> mixture is either too rich, or something is going haywire with the
> timing & causing the fuel to not burn at higher RPM. One thing worth
> noting, is that I have not changed the plugs since they have been
> fouled since I replaced the faulty vacuum advance. I didn't know if
> this would make a difference or not & didn't want to risk fouling a
> new set while troubleshooting. I can literally get flames to shoot
> out of my exhaust if I abuse it enough. This happens on both sides &
> I have dual exhaust, leading me to think it's not a valve issue,
> unless I'm really unlucky & have a problem on both sides of the
> engine.
>
> The jeep is a recreational vehicle of sorts, used primarily to climb
> up & down sand dunes. The symptoms all occured when my fuel pump died
> about 2 years ago. After I replaced the pump, the engine started
> doing this. I've since replaced it again to rule that out with no
> change. I've also rebuilt the carburetor, but it was the first time I
> ever did such a thing, so it's quite possible I missed something. The
> accelerator pump works fine, the idle mixture screws are set very lean
> (since I think the mixture is too rich for some reason), the power
> valve has been replaced & I even checked it again last week & I can
> see spray coming out of the booster venturi when I rev the engine (it
> does this whether I'm moving or not). Another thing I noticed is that
> when the engine is cold, if I hold my hand in front of the exhaust, it
> sprays black fluid on me at idle. It's not a lot, but I noticed it
> when it was sprayed on my leg one day. It has no smell to it other
> than stinky exhaust, so I don't really know what this is. My coolant
> level has not changed noticeably, so I wouldn't think it to be a water
> leak, but I can't say with certainty.
>
> Here are the basics:
> 1972 Jeep CJ5
> AMC 304
> Aftermarket parts:
> Edlebrock peformer intake
> Holley 600cfm 4-bbl carb
> Edlebrock shorty headers
>
> Thanks for any help you guys can give on this. I'm at a loss & don't
> know what to do next.
>
> -Matt
>

Re: CJ5 misfires at high RPM/hard acceleration
 

If the plugs are just fouled, I would pull them out and clean them up with
some light brushing and some B-12chemtool. Re-gap, re-install, and see if
that helps.

Carl


<matthew.nye@gmail.com> wrote in message
news:1184524973.150369.268860@22g2000hsm.googlegro ups.com...
> Gentlemen,
>
> I'm having some problems tracking this down. When I accelerate hard
> or get up to a certain RPM (about 3000) at cruising, I get popping
> coming out of my exhaust & a huge lack in power. The engine has never
> stalled, but I can't go any faster in that gear due to the misfiring.
> I've done almost everything that I can think of short of checking the
> timing chain & replacing the carburetor. Here's what I've done so
> far:
>
> Changed coil + ballast resistor + ignition wires/wire to distributor
> Changed fuel filter + replaced all fuel lines
> Changed fuel pump
> Changed points + condenser
> Changed plugs + plug wires (plugs gapped at .035)
> Changed cap + rotor
> Changed vacuum advance (this was confirmed bad & made a huge
> difference)
>
> The initial timing is 6 degrees BTDC & the dwell angle is about 31. I
> get about 16hg of steady vacuum at idle & about 7psi of fuel pressure
> at idle. The idle & even light acceleration is perfect, which makes
> me think it's not a timing chain issue, but I don't know enough about
> what the symptoms of a slipped chain would be to make that call. When
> the engine is at TDC of piston 1's compression stroke, the rotor lines
> up perfectly with cylinder 1's plug wire, which also makes me thing
> it's not necessarily a timing chain issue. Since I have changed the
> plugs & tried to further diagnose the problem, my plugs have turned
> black. This along with the popping in the exhaust obviously mean my
> mixture is either too rich, or something is going haywire with the
> timing & causing the fuel to not burn at higher RPM. One thing worth
> noting, is that I have not changed the plugs since they have been
> fouled since I replaced the faulty vacuum advance. I didn't know if
> this would make a difference or not & didn't want to risk fouling a
> new set while troubleshooting. I can literally get flames to shoot
> out of my exhaust if I abuse it enough. This happens on both sides &
> I have dual exhaust, leading me to think it's not a valve issue,
> unless I'm really unlucky & have a problem on both sides of the
> engine.
>
> The jeep is a recreational vehicle of sorts, used primarily to climb
> up & down sand dunes. The symptoms all occured when my fuel pump died
> about 2 years ago. After I replaced the pump, the engine started
> doing this. I've since replaced it again to rule that out with no
> change. I've also rebuilt the carburetor, but it was the first time I
> ever did such a thing, so it's quite possible I missed something. The
> accelerator pump works fine, the idle mixture screws are set very lean
> (since I think the mixture is too rich for some reason), the power
> valve has been replaced & I even checked it again last week & I can
> see spray coming out of the booster venturi when I rev the engine (it
> does this whether I'm moving or not). Another thing I noticed is that
> when the engine is cold, if I hold my hand in front of the exhaust, it
> sprays black fluid on me at idle. It's not a lot, but I noticed it
> when it was sprayed on my leg one day. It has no smell to it other
> than stinky exhaust, so I don't really know what this is. My coolant
> level has not changed noticeably, so I wouldn't think it to be a water
> leak, but I can't say with certainty.
>
> Here are the basics:
> 1972 Jeep CJ5
> AMC 304
> Aftermarket parts:
> Edlebrock peformer intake
> Holley 600cfm 4-bbl carb
> Edlebrock shorty headers
>
> Thanks for any help you guys can give on this. I'm at a loss & don't
> know what to do next.
>
> -Matt
>

Re: CJ5 misfires at high RPM/hard acceleration
 

How is the gas tank air vent filter?

It will kill the top end and act very strange when this gets blocked.

It is a $2.00 'emissions' filter on the bottom of the charcoal canister.

To test this, just drive with the gas cap loose or off and see what happens.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's - Gone to the rust pile...
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)

matthew.nye@gmail.com wrote:
> Gentlemen,

>

Re: CJ5 misfires at high RPM/hard acceleration
 

How is the gas tank air vent filter?

It will kill the top end and act very strange when this gets blocked.

It is a $2.00 'emissions' filter on the bottom of the charcoal canister.

To test this, just drive with the gas cap loose or off and see what happens.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's - Gone to the rust pile...
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)

matthew.nye@gmail.com wrote:
> Gentlemen,

>

Re: CJ5 misfires at high RPM/hard acceleration
 

How is the gas tank air vent filter?

It will kill the top end and act very strange when this gets blocked.

It is a $2.00 'emissions' filter on the bottom of the charcoal canister.

To test this, just drive with the gas cap loose or off and see what happens.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's - Gone to the rust pile...
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)

matthew.nye@gmail.com wrote:
> Gentlemen,

>

Re: CJ5 misfires at high RPM/hard acceleration
 

How is the gas tank air vent filter?

It will kill the top end and act very strange when this gets blocked.

It is a $2.00 'emissions' filter on the bottom of the charcoal canister.

To test this, just drive with the gas cap loose or off and see what happens.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's - Gone to the rust pile...
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)

matthew.nye@gmail.com wrote:
> Gentlemen,

>

Re: CJ5 misfires at high RPM/hard acceleration
 

In article <1184524973.150369.268860@22g2000hsm.googlegroups. com>,
<matthew.nye@gmail.com> wrote:

> Gentlemen,
>
> I'm having some problems tracking this down. When I accelerate hard
> or get up to a certain RPM (about 3000) at cruising, I get popping
> coming out of my exhaust & a huge lack in power. The engine has never
> stalled, but I can't go any faster in that gear due to the misfiring.
> I've done almost everything that I can think of short of checking the
> timing chain & replacing the carburetor. Here's what I've done so
> far:

Try driving with the coil "+" terminal jumped straight to the
battery to eliminate the possibility that there is an amperage loss
through the ignition switch. Also, the old fuel pump may have send
diaphragm chunks into the carb. How well did you blow out the passages?

I suppose it is possible that a pump seizing against the eccentric on
a worn chain may have caused a tooth jump. If this is the original
chain, it might be worth the time to change it anyway.

>
> Changed coil + ballast resistor + ignition wires/wire to distributor
> Changed fuel filter + replaced all fuel lines
> Changed fuel pump
> Changed points + condenser
> Changed plugs + plug wires (plugs gapped at .035)
> Changed cap + rotor
> Changed vacuum advance (this was confirmed bad & made a huge
> difference)
>
> The initial timing is 6 degrees BTDC & the dwell angle is about 31. I
> get about 16hg of steady vacuum at idle & about 7psi of fuel pressure
> at idle. The idle & even light acceleration is perfect, which makes
> me think it's not a timing chain issue, but I don't know enough about
> what the symptoms of a slipped chain would be to make that call. When
> the engine is at TDC of piston 1's compression stroke, the rotor lines
> up perfectly with cylinder 1's plug wire, which also makes me thing
> it's not necessarily a timing chain issue. Since I have changed the
> plugs & tried to further diagnose the problem, my plugs have turned
> black. This along with the popping in the exhaust obviously mean my
> mixture is either too rich, or something is going haywire with the
> timing & causing the fuel to not burn at higher RPM. One thing worth
> noting, is that I have not changed the plugs since they have been
> fouled since I replaced the faulty vacuum advance. I didn't know if
> this would make a difference or not & didn't want to risk fouling a
> new set while troubleshooting. I can literally get flames to shoot
> out of my exhaust if I abuse it enough. This happens on both sides &
> I have dual exhaust, leading me to think it's not a valve issue,
> unless I'm really unlucky & have a problem on both sides of the
> engine.
>
> The jeep is a recreational vehicle of sorts, used primarily to climb
> up & down sand dunes. The symptoms all occured when my fuel pump died
> about 2 years ago. After I replaced the pump, the engine started
> doing this. I've since replaced it again to rule that out with no
> change. I've also rebuilt the carburetor, but it was the first time I
> ever did such a thing, so it's quite possible I missed something. The
> accelerator pump works fine, the idle mixture screws are set very lean
> (since I think the mixture is too rich for some reason), the power
> valve has been replaced & I even checked it again last week & I can
> see spray coming out of the booster venturi when I rev the engine (it
> does this whether I'm moving or not). Another thing I noticed is that
> when the engine is cold, if I hold my hand in front of the exhaust, it
> sprays black fluid on me at idle. It's not a lot, but I noticed it
> when it was sprayed on my leg one day. It has no smell to it other
> than stinky exhaust, so I don't really know what this is. My coolant
> level has not changed noticeably, so I wouldn't think it to be a water
> leak, but I can't say with certainty.
>
> Here are the basics:
> 1972 Jeep CJ5
> AMC 304
> Aftermarket parts:
> Edlebrock peformer intake
> Holley 600cfm 4-bbl carb
> Edlebrock shorty headers
>
> Thanks for any help you guys can give on this. I'm at a loss & don't
> know what to do next.
>
> -Matt
>

--
CobraJet