New to the forum, been searching for a few days but no real answer or ideas to my issue. Acquired a '94 grand cherokee laredo a few months ago, was given to me and told I could have it to see if I could get it to run.

Issue: Runs perfect, no miss, couldn't be better for approx. 5-6 miles or sitting idling for about 20 minutes. Everything all good, then it starts to miss, then gets worse, then pop, backfire to the point if you give it gas it doesn't have enough power to move itself. If you turn it off and let it sit for half hour and cool off it will repeat process. It seems to get really rich and has backfired enough to blow the muffler apart, always seems to be backfiring out the exhaust and not in the intake area.

To date I have installed a new fuel pump and filter because pressure wasn't great (now has good pressure), replaced the ECU (no change), camshaft sensor, plugs, wires, coil. Does not throw a code at all, nothing. Cat was removed also to verify not clogged.

I have not replaced the O2, map sensor or crank sensor as of yet. Just makes me beat my head how great it can run for that period of time and then just go to running terrible.

Any ideas would be great, nothing worse than an unknown problem that is intermittent.

 

sounds like a bad crank sensor, and as soon as you can you should have that cat re-installed or replaced with a new one.

 

You may as well get a rebuilt engine to install.

 

Why?