1990 Cherokee 4.0 backfire misfire help. - Pirate4x4.Com : 4x4 and Off-Road Forum

hillaholic · 05-13-2009, 12:06 PM

Sorry for the long post but I’m about to scrap this if I can’t fix it.

I have a 1990 Cherokee Limited with a 4.0, automatic with 130k miles. And I am having problem with it backfiring when I let off the gas when driving. If I rev it up in neutral it also hesitates and misfires/shakes badly. The fuel economy is also bad, I was getting about 16mpg now I’m getting 12mpg.

This is a list of what I have replaced recently.
Exhaust, from the manifold back including new converter.
O2 sensor
Intake/Exhaust manifold gasket.
Fuel filter
New distributor, distributor cap, plugs, wires
Water pump
Radiator
Harmonic balancer pulley.

I replaced the distributor because the old one was oscillating badly when running. The remanufactured one I put in still oscillates but not nearly as bad. I just got another remanufactured distributor to replace the other one thinking that’s the problem but haven’t installed it yet.

Any and all help is much appreciated, Brad

xo_jeep · 05-13-2009, 12:22 PM

Quote:

Originally Posted by hillaholic

Sorry for posting in the wrong section...

Fixed

trickcomanche · 05-13-2009, 02:44 PM

Check your timing.

hillaholic · 05-13-2009, 02:58 PM

Is there a way to adjust it? I put the distributor in by the book about 10 times because I thought it was off a little. It will only start in one position and how the distributor mounts how do you adjust it?

trickcomanche · 05-13-2009, 03:08 PM

Loosen the bolt that holds it down and try to rotate it while the jeep is running. See what happends.

trickcomanche · 05-13-2009, 03:09 PM

Check for leaks @ yer manifolg gaskets too.

hillaholic · 05-13-2009, 04:00 PM

Quote:

Originally Posted by trickcomanche

Loosen the bolt that holds it down and try to rotate it while the jeep is running. See what happends.

You can't rotate it. It has a U formed into the distributor that the bolt goes through. I tried taking the bolt out and holding the distributor in by hand, but when you try to start it pushes it out. Is a bent distributor a common thing on the 4.0?

hillaholic · 05-13-2009, 04:03 PM

Quote:

Originally Posted by trickcomanche

Check for leaks @ yer manifolg gaskets too.

I just replaced it. I sprayed carb cleaner everywhere looking for a vacuum leak and no change in engine noise

DESracing · 05-13-2009, 04:24 PM

Are you sure the motor is good? No burnt valves or broken springs etc....

hillaholic · 05-13-2009, 09:13 PM

Quote:

Originally Posted by DESracing

Are you sure the motor is good? No burnt valves or broken springs etc....

I'm not sure how do I test for that?

hillaholic · 05-15-2009, 11:50 AM

I finally got it running right. I put another remanufactured distributor in and it runs perfect. What a PITA all the stuff I replaced and it was a bad new distributor.

The new distributor still oscillates when it’s running. What would cause this?

Alfred W. · 05-16-2009, 09:49 PM

Quote:

Originally Posted by hillaholic

I finally got it running right. I put another remanufactured distributor in and it runs perfect. What a PITA all the stuff I replaced and it was a bad new distributor.

The new distributor still oscillates when it’s running. What would cause this?

A video would help with this one.

05-13-2009, 12:06 PM	#1 (permalink)
hillaholic Registered User Join Date: Jan 2009 Member # 126786 Location: Elyria, OH Posts: 10	1990 Cherokee 4.0 backfire misfire help. Sorry for the long post but I’m about to scrap this if I can’t fix it. I have a 1990 Cherokee Limited with a 4.0, automatic with 130k miles. And I am having problem with it backfiring when I let off the gas when driving. If I rev it up in neutral it also hesitates and misfires/shakes badly. The fuel economy is also bad, I was getting about 16mpg now I’m getting 12mpg. This is a list of what I have replaced recently. Exhaust, from the manifold back including new converter. O2 sensor Intake/Exhaust manifold gasket. Fuel filter New distributor, distributor cap, plugs, wires Water pump Radiator Harmonic balancer pulley. I replaced the distributor because the old one was oscillating badly when running. The remanufactured one I put in still oscillates but not nearly as bad. I just got another remanufactured distributor to replace the other one thinking that’s the problem but haven’t installed it yet. Any and all help is much appreciated, Brad

05-13-2009, 02:44 PM	#3 (permalink)
trickcomanche Registered User Join Date: Nov 2007 Member # 102300 Location: NE UT Posts: 366	Check your timing. __________________ BUILD IT, RUN IT, BREAKE IT, REPETE

05-13-2009, 03:08 PM	#5 (permalink)
trickcomanche Registered User Join Date: Nov 2007 Member # 102300 Location: NE UT Posts: 366	Loosen the bolt that holds it down and try to rotate it while the jeep is running. See what happends. __________________ BUILD IT, RUN IT, BREAKE IT, REPETE

05-13-2009, 03:09 PM	#6 (permalink)
trickcomanche Registered User Join Date: Nov 2007 Member # 102300 Location: NE UT Posts: 366	Check for leaks @ yer manifolg gaskets too. __________________ BUILD IT, RUN IT, BREAKE IT, REPETE

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05-13-2009, 02:58 PM	#4 (permalink)
hillaholic Registered User Join Date: Jan 2009 Member # 126786 Location: Elyria, OH Posts: 10	Is there a way to adjust it? I put the distributor in by the book about 10 times because I thought it was off a little. It will only start in one position and how the distributor mounts how do you adjust it?

05-13-2009, 04:24 PM	#9 (permalink)
DESracing Registered User Join Date: Oct 2006 Member # 80470 Location: Oc Posts: 528	Are you sure the motor is good? No burnt valves or broken springs etc....

05-15-2009, 11:50 AM	#11 (permalink)
hillaholic Registered User Join Date: Jan 2009 Member # 126786 Location: Elyria, OH Posts: 10	I finally got it running right. I put another remanufactured distributor in and it runs perfect. What a PITA all the stuff I replaced and it was a bad new distributor. The new distributor still oscillates when it’s running. What would cause this?