I have a 96 zj 4.0. Bought it for $600 after a severe overheat (was driven about 30 miles after radiator/water pump failed and leaked all coolant). I've replaced the cracked head, cracked exhaust manifold, entire cooling system, entire ignition system from computer to plugs, tps, iac, hollow cat and exploded muffler. It's running pretty damn good now aside from a slightly rough idle in any gear. My rpm's seem to have a variance of around 400 from the lowest to highest point at idle. It doesn't die, sputter or backfire at idle or driving. However, if I throttle up to any rpm while parked and hold the accelerator in the same spot, my rpms will steadily start to drop. Once they've dropped a fair amount, if I let off the accelerator suddenly, the rpms drop to zero and the jeep dies. If I gradually let off, it will compensate and hold idle. Any thoughts? This bouncing needle is my last bug to work out (for now) and it's driving me nuts!

 

Need to post here:

https://www.cherokeeforum.com/f5/

 

Had the same issue with my 96 about 4 years ago. I want to say it was the crank sensor was the final fix but now I'm trying to remember if that was my 03. Same symptoms rough idle would die all plugs replaced new battery etc.

 

Thanks hatch, that's what I was leaning towards too. I'll give it a shot.