Re: 4.0 light miss
 

On Fri, 6 Oct 2006 17:07:57 UTC "JeffDeWitt" <jeffdewitt@gmail.com>
wrote:

>
> DougW wrote:
> > Jeffrey DeWitt wrote:
> > > Gang,
> > >
> > > My good old 96 Cherokee has a slight miss, and has had it since the
> > > new engine was put in.
> >
> > I had a slight miss on my 93 4.0 for quite a while and it turned out
> > to be the coil assembly. Coil and resistance wire were a recall for
> > several years and if you don't have the correct one it seems to throw
> > the timing off. Dunno exacly how, but it did solve my problem.
> > http://partimages2.genpt.com/partimages/103447.jpg
> >
> > The ZJ can now run 91 with no problem.. keep in mind my 4.0 has a blower
> > and prior to this I had to run 93 or suffer highway ping.
> >
> > And also the fuel filter, but usually that is ping only at full throttle.
> >
> > --
> > DougW
>
> I've got no problem replacing the coil if that will fix it, but if it
> is the coil why will the engine sometimes run better with injector
> cleaner in it, and why did it run so well for a few min. while the
> computer was resetting?

You might want to check the fuel pressure on the rail as well -
marginal pressure or low pump capacity can cause what you see as well.

--
Will Honea

Re: 4.0 light miss
 

On Fri, 6 Oct 2006 17:07:57 UTC "JeffDeWitt" <jeffdewitt@gmail.com>
wrote:

>
> DougW wrote:
> > Jeffrey DeWitt wrote:
> > > Gang,
> > >
> > > My good old 96 Cherokee has a slight miss, and has had it since the
> > > new engine was put in.
> >
> > I had a slight miss on my 93 4.0 for quite a while and it turned out
> > to be the coil assembly. Coil and resistance wire were a recall for
> > several years and if you don't have the correct one it seems to throw
> > the timing off. Dunno exacly how, but it did solve my problem.
> > http://partimages2.genpt.com/partimages/103447.jpg
> >
> > The ZJ can now run 91 with no problem.. keep in mind my 4.0 has a blower
> > and prior to this I had to run 93 or suffer highway ping.
> >
> > And also the fuel filter, but usually that is ping only at full throttle.
> >
> > --
> > DougW
>
> I've got no problem replacing the coil if that will fix it, but if it
> is the coil why will the engine sometimes run better with injector
> cleaner in it, and why did it run so well for a few min. while the
> computer was resetting?

You might want to check the fuel pressure on the rail as well -
marginal pressure or low pump capacity can cause what you see as well.

--
Will Honea

Re: 4.0 light miss
 

On Fri, 6 Oct 2006 17:07:57 UTC "JeffDeWitt" <jeffdewitt@gmail.com>
wrote:

>
> DougW wrote:
> > Jeffrey DeWitt wrote:
> > > Gang,
> > >
> > > My good old 96 Cherokee has a slight miss, and has had it since the
> > > new engine was put in.
> >
> > I had a slight miss on my 93 4.0 for quite a while and it turned out
> > to be the coil assembly. Coil and resistance wire were a recall for
> > several years and if you don't have the correct one it seems to throw
> > the timing off. Dunno exacly how, but it did solve my problem.
> > http://partimages2.genpt.com/partimages/103447.jpg
> >
> > The ZJ can now run 91 with no problem.. keep in mind my 4.0 has a blower
> > and prior to this I had to run 93 or suffer highway ping.
> >
> > And also the fuel filter, but usually that is ping only at full throttle.
> >
> > --
> > DougW
>
> I've got no problem replacing the coil if that will fix it, but if it
> is the coil why will the engine sometimes run better with injector
> cleaner in it, and why did it run so well for a few min. while the
> computer was resetting?

You might want to check the fuel pressure on the rail as well -
marginal pressure or low pump capacity can cause what you see as well.

--
Will Honea

Re: 4.0 light miss
 

I might go ahead and put a new coil on anyway, it's easy and it IS the
orginal coil so it shouldn't hurt to put in a new one, and as Doug
points out it's not bad to have a spare.

I've also wondered about that fuel pump, it's orginal too, looks like a
new pump is about $100 and a gage to check the old one is about $35 so
maybe it would be a good idea to just replace the pump but I can't say
I'm thrilled about the idea... somehow I expect that pump is a LOT
harder to replace than the one on my Studebaker truck (two fittings,
two bolts, 15 min.).

Jeff DeWitt
Will Honea wrote:
> On Fri, 6 Oct 2006 17:07:57 UTC "JeffDeWitt" <jeffdewitt@gmail.com>
> wrote:
>
> >
> > DougW wrote:
> > > Jeffrey DeWitt wrote:
> > > > Gang,
> > > >
> > > > My good old 96 Cherokee has a slight miss, and has had it since the
> > > > new engine was put in.
> > >
> > > I had a slight miss on my 93 4.0 for quite a while and it turned out
> > > to be the coil assembly. Coil and resistance wire were a recall for
> > > several years and if you don't have the correct one it seems to throw
> > > the timing off. Dunno exacly how, but it did solve my problem.
> > > http://partimages2.genpt.com/partimages/103447.jpg
> > >
> > > The ZJ can now run 91 with no problem.. keep in mind my 4.0 has a blower
> > > and prior to this I had to run 93 or suffer highway ping.
> > >
> > > And also the fuel filter, but usually that is ping only at full throttle.
> > >
> > > --
> > > DougW
> >
> > I've got no problem replacing the coil if that will fix it, but if it
> > is the coil why will the engine sometimes run better with injector
> > cleaner in it, and why did it run so well for a few min. while the
> > computer was resetting?
>
> You might want to check the fuel pressure on the rail as well -
> marginal pressure or low pump capacity can cause what you see as well.
>
> --
> Will Honea

Re: 4.0 light miss
 

I might go ahead and put a new coil on anyway, it's easy and it IS the
orginal coil so it shouldn't hurt to put in a new one, and as Doug
points out it's not bad to have a spare.

I've also wondered about that fuel pump, it's orginal too, looks like a
new pump is about $100 and a gage to check the old one is about $35 so
maybe it would be a good idea to just replace the pump but I can't say
I'm thrilled about the idea... somehow I expect that pump is a LOT
harder to replace than the one on my Studebaker truck (two fittings,
two bolts, 15 min.).

Jeff DeWitt
Will Honea wrote:
> On Fri, 6 Oct 2006 17:07:57 UTC "JeffDeWitt" <jeffdewitt@gmail.com>
> wrote:
>
> >
> > DougW wrote:
> > > Jeffrey DeWitt wrote:
> > > > Gang,
> > > >
> > > > My good old 96 Cherokee has a slight miss, and has had it since the
> > > > new engine was put in.
> > >
> > > I had a slight miss on my 93 4.0 for quite a while and it turned out
> > > to be the coil assembly. Coil and resistance wire were a recall for
> > > several years and if you don't have the correct one it seems to throw
> > > the timing off. Dunno exacly how, but it did solve my problem.
> > > http://partimages2.genpt.com/partimages/103447.jpg
> > >
> > > The ZJ can now run 91 with no problem.. keep in mind my 4.0 has a blower
> > > and prior to this I had to run 93 or suffer highway ping.
> > >
> > > And also the fuel filter, but usually that is ping only at full throttle.
> > >
> > > --
> > > DougW
> >
> > I've got no problem replacing the coil if that will fix it, but if it
> > is the coil why will the engine sometimes run better with injector
> > cleaner in it, and why did it run so well for a few min. while the
> > computer was resetting?
>
> You might want to check the fuel pressure on the rail as well -
> marginal pressure or low pump capacity can cause what you see as well.
>
> --
> Will Honea

Re: 4.0 light miss
 

I might go ahead and put a new coil on anyway, it's easy and it IS the
orginal coil so it shouldn't hurt to put in a new one, and as Doug
points out it's not bad to have a spare.

I've also wondered about that fuel pump, it's orginal too, looks like a
new pump is about $100 and a gage to check the old one is about $35 so
maybe it would be a good idea to just replace the pump but I can't say
I'm thrilled about the idea... somehow I expect that pump is a LOT
harder to replace than the one on my Studebaker truck (two fittings,
two bolts, 15 min.).

Jeff DeWitt
Will Honea wrote:
> On Fri, 6 Oct 2006 17:07:57 UTC "JeffDeWitt" <jeffdewitt@gmail.com>
> wrote:
>
> >
> > DougW wrote:
> > > Jeffrey DeWitt wrote:
> > > > Gang,
> > > >
> > > > My good old 96 Cherokee has a slight miss, and has had it since the
> > > > new engine was put in.
> > >
> > > I had a slight miss on my 93 4.0 for quite a while and it turned out
> > > to be the coil assembly. Coil and resistance wire were a recall for
> > > several years and if you don't have the correct one it seems to throw
> > > the timing off. Dunno exacly how, but it did solve my problem.
> > > http://partimages2.genpt.com/partimages/103447.jpg
> > >
> > > The ZJ can now run 91 with no problem.. keep in mind my 4.0 has a blower
> > > and prior to this I had to run 93 or suffer highway ping.
> > >
> > > And also the fuel filter, but usually that is ping only at full throttle.
> > >
> > > --
> > > DougW
> >
> > I've got no problem replacing the coil if that will fix it, but if it
> > is the coil why will the engine sometimes run better with injector
> > cleaner in it, and why did it run so well for a few min. while the
> > computer was resetting?
>
> You might want to check the fuel pressure on the rail as well -
> marginal pressure or low pump capacity can cause what you see as well.
>
> --
> Will Honea

Re: 4.0 light miss
 

I might go ahead and put a new coil on anyway, it's easy and it IS the
orginal coil so it shouldn't hurt to put in a new one, and as Doug
points out it's not bad to have a spare.

I've also wondered about that fuel pump, it's orginal too, looks like a
new pump is about $100 and a gage to check the old one is about $35 so
maybe it would be a good idea to just replace the pump but I can't say
I'm thrilled about the idea... somehow I expect that pump is a LOT
harder to replace than the one on my Studebaker truck (two fittings,
two bolts, 15 min.).

Jeff DeWitt
Will Honea wrote:
> On Fri, 6 Oct 2006 17:07:57 UTC "JeffDeWitt" <jeffdewitt@gmail.com>
> wrote:
>
> >
> > DougW wrote:
> > > Jeffrey DeWitt wrote:
> > > > Gang,
> > > >
> > > > My good old 96 Cherokee has a slight miss, and has had it since the
> > > > new engine was put in.
> > >
> > > I had a slight miss on my 93 4.0 for quite a while and it turned out
> > > to be the coil assembly. Coil and resistance wire were a recall for
> > > several years and if you don't have the correct one it seems to throw
> > > the timing off. Dunno exacly how, but it did solve my problem.
> > > http://partimages2.genpt.com/partimages/103447.jpg
> > >
> > > The ZJ can now run 91 with no problem.. keep in mind my 4.0 has a blower
> > > and prior to this I had to run 93 or suffer highway ping.
> > >
> > > And also the fuel filter, but usually that is ping only at full throttle.
> > >
> > > --
> > > DougW
> >
> > I've got no problem replacing the coil if that will fix it, but if it
> > is the coil why will the engine sometimes run better with injector
> > cleaner in it, and why did it run so well for a few min. while the
> > computer was resetting?
>
> You might want to check the fuel pressure on the rail as well -
> marginal pressure or low pump capacity can cause what you see as well.
>
> --
> Will Honea

Re: 4.0 light miss
 

I might go ahead and put a new coil on anyway, it's easy and it IS the
orginal coil so it shouldn't hurt to put in a new one, and as Doug
points out it's not bad to have a spare.

I've also wondered about that fuel pump, it's orginal too, looks like a
new pump is about $100 and a gage to check the old one is about $35 so
maybe it would be a good idea to just replace the pump but I can't say
I'm thrilled about the idea... somehow I expect that pump is a LOT
harder to replace than the one on my Studebaker truck (two fittings,
two bolts, 15 min.).

Jeff DeWitt
Will Honea wrote:
> On Fri, 6 Oct 2006 17:07:57 UTC "JeffDeWitt" <jeffdewitt@gmail.com>
> wrote:
>
> >
> > DougW wrote:
> > > Jeffrey DeWitt wrote:
> > > > Gang,
> > > >
> > > > My good old 96 Cherokee has a slight miss, and has had it since the
> > > > new engine was put in.
> > >
> > > I had a slight miss on my 93 4.0 for quite a while and it turned out
> > > to be the coil assembly. Coil and resistance wire were a recall for
> > > several years and if you don't have the correct one it seems to throw
> > > the timing off. Dunno exacly how, but it did solve my problem.
> > > http://partimages2.genpt.com/partimages/103447.jpg
> > >
> > > The ZJ can now run 91 with no problem.. keep in mind my 4.0 has a blower
> > > and prior to this I had to run 93 or suffer highway ping.
> > >
> > > And also the fuel filter, but usually that is ping only at full throttle.
> > >
> > > --
> > > DougW
> >
> > I've got no problem replacing the coil if that will fix it, but if it
> > is the coil why will the engine sometimes run better with injector
> > cleaner in it, and why did it run so well for a few min. while the
> > computer was resetting?
>
> You might want to check the fuel pressure on the rail as well -
> marginal pressure or low pump capacity can cause what you see as well.
>
> --
> Will Honea

Re: 4.0 light miss
 

I might go ahead and put a new coil on anyway, it's easy and it IS the
orginal coil so it shouldn't hurt to put in a new one, and as Doug
points out it's not bad to have a spare.

I've also wondered about that fuel pump, it's orginal too, looks like a
new pump is about $100 and a gage to check the old one is about $35 so
maybe it would be a good idea to just replace the pump but I can't say
I'm thrilled about the idea... somehow I expect that pump is a LOT
harder to replace than the one on my Studebaker truck (two fittings,
two bolts, 15 min.).

Jeff DeWitt
Will Honea wrote:
> On Fri, 6 Oct 2006 17:07:57 UTC "JeffDeWitt" <jeffdewitt@gmail.com>
> wrote:
>
> >
> > DougW wrote:
> > > Jeffrey DeWitt wrote:
> > > > Gang,
> > > >
> > > > My good old 96 Cherokee has a slight miss, and has had it since the
> > > > new engine was put in.
> > >
> > > I had a slight miss on my 93 4.0 for quite a while and it turned out
> > > to be the coil assembly. Coil and resistance wire were a recall for
> > > several years and if you don't have the correct one it seems to throw
> > > the timing off. Dunno exacly how, but it did solve my problem.
> > > http://partimages2.genpt.com/partimages/103447.jpg
> > >
> > > The ZJ can now run 91 with no problem.. keep in mind my 4.0 has a blower
> > > and prior to this I had to run 93 or suffer highway ping.
> > >
> > > And also the fuel filter, but usually that is ping only at full throttle.
> > >
> > > --
> > > DougW
> >
> > I've got no problem replacing the coil if that will fix it, but if it
> > is the coil why will the engine sometimes run better with injector
> > cleaner in it, and why did it run so well for a few min. while the
> > computer was resetting?
>
> You might want to check the fuel pressure on the rail as well -
> marginal pressure or low pump capacity can cause what you see as well.
>
> --
> Will Honea

Re: 4.0 light miss
 

JeffDeWitt wrote:
> I might go ahead and put a new coil on anyway, it's easy and it IS the
> orginal coil so it shouldn't hurt to put in a new one, and as Doug
> points out it's not bad to have a spare.

Double check the part but I used the NAPA part ECHIC409. It's the
same one that was used for a recall Jeep had a long time back. Comes
with a coil and adapter harness. You have to use the harness with this
coil as it contains a balast resistor.

Other than that it depends on if you have blades or pins. My factory
connector is pins, the later model is blade.

> I've also wondered about that fuel pump, it's orginal too, looks like
> a new pump is about $100 and a gage to check the old one is about $35
> so maybe it would be a good idea to just replace the pump but I can't
> say I'm thrilled about the idea... somehow I expect that pump is a LOT
> harder to replace than the one on my Studebaker truck (two fittings,
> two bolts, 15 min.).

Fuel pump pressure is easy to check if you have an old R-12 gauge
or stop by autozone (or sears) and buy one. Just hook it up and
duct tape it to the windshield.

My pump still works. Generally if the filter is clogged or the pump is
shot, you will get real bad ping under load and at wide-open-throttle.
Both times I've gotten ping at WOT it's been due to a clogged filter.
http://revbeergoggles.com/badgas/


--
DougW