I have a 1996 Jeep Grand Cherokee 4x4, 6cyl with 125000. Over the last 3 weeks I have had it into 3 different shops trying to fix my missfiring problem.

It only missfires when the engine is cold, once the engine is up to operating temp it runs like a champ. We have looked at everything you can think of from sensors, distributor, fuel pump even the master computer.

Anyone have any ideas to help?

Does the CHECK ENGINE light come on?

It sounds like an Air/fuel ration mixture problem and after the engine warms, the O2 Sensor comes into play and straighten out the mixture.

The computer uses the O2 Sensor to detected Rich/Lean mixture but only after engine is completely warmed (Actually, after the O2 Sensor reached normal operating tempature of 600+ degrees) during the warm up period the Fuel Pump is on an open loop. you might want to check Fuel Pressure when engine is cold.

If I think of anything else I will repost.

Yes, the check engine light does come on while it is misfiring/chugging. Engine light goes off when I shut off the ignition. It only misfires when I give it gas. It will not misfire when it is idling. Very strange.

It misfires for about 3-5 minites then it seems to work everything out on its own and then runs like a champ the rest of the day. Even when i turn off the Jeep and start back up later it runs fine. Engine temp is still warm in most cases.

Does this help more?

Does the CHECK ENGINE light come on?

It sounds like an Air/fuel ration mixture problem and after the engine warms, the O2 Sensor comes into play and straighten out the mixture.

The computer uses the O2 Sensor to detected Rich/Lean mixture but only after engine is completely warmed (Actually, after the O2 Sensor reached normal operating tempature of 600+ degrees) during the warm up period the Fuel Pump is on an open loop. you might want to check Fuel Pressure when engine is cold.

If I think of anything else I will repost.

have you had the CODES checked to see what pops up?

You could take it to AUTOZONE while the CHECK ENGINE light is on and they can scan it, or the dealership and they can scan the computer for any stored codes.

Yes, they have scanned it and it only tells them that all 8 cyclders are missing. The code does not point to a specific target.

The jeep runs fine in an open loop but as soon as the loop closes it starts misfiring for maybe 3-5 minutes under gas then stops and runs like a champ rest of the day. It does NOT misfire at idle during that same 3-5 minutes period. Hope this helps define my problem better.

have you had the CODES checked to see what pops up?

You could take it to AUTOZONE while the CHECK ENGINE light is on and they can scan it, or the dealership and they can scan the computer for any stored codes.

June 27. Any solution to this problem yet ?

June 27. Any solution to this problem yet ?