Has anybody dealt with this? Ok... I'm pretty good with diagnosis but this one has me stumped. I have a 95 Grand Cherokee Laredo. It initially started while I was in the process of changing sensors related to shifting issues with a new transmission. After you start the vehicle it will idle normally for about 5 min. Then misfire for several min and return to normal idle. It will repeat this for 4 cycles, each misfire cycle being worse than the one before. This will take about 20 min to go through this and then will run fine after. It is very consistant. I did find bad ignition parts and replaced everything but the misfire continues. When you put a timming light on the spark plug wires you will see the misfire on all 6 cylinders. You can see the misfire on the primary directly from the coil. The jeep dealer sugests carbon buildup sticking the valves and I have tried various decarbonizing treatments with no change. At this point all the sensors have been replaced or swaped with working sensors but nothing changes. I don't have a spare computer to try, so I can't try that and there are no codes strored to give me a clue. Any ideas people. I don't like taking it to the dealer because they always break something and I end up fixing it anyway...

 

I had something simular happen, not as severe as yours... but i replaced EVERY SENSOR PLUGS LINES EVERYTHING...

And it ended up being the COMPUTER.

Bought a refurb for about $250 and it has ran fine since.

GOOD LUCK!

-Nate