New to the forum.. Thanks in advance for your help.


1996 Jeep Grand Cherokee Laredo 4.0L auto 169,000 miles


It is starting to idle rough and die at times. Can't predict when and it (so far) always starts right back up but it is getting a bit worrisome. My wife is worried she's going to get stranded somewhere.


Background - did this a year or so ago. Seems to coincide with the time of year (I live in Houston and it seems to only occur in summer when hot). I couldn't figure it out last year. It did it to me once or twice and then never did it again.


Earlier this spring - tuned it up; plugs, wires, distributor cap, coil and coil wire. Ran great (and still does for the most part).


6-8 weeks ago - just as it starts getting HOT! here. Sitting in traffic and it's like someone reaches over and turns the ignition off. No rough idle beforehand that I noticed anyway. Happens a couple time. Replace the crankshaft sensor a month or so ago. Everything is good.


A week ago - my wife is driving it and it starts idling rough and dies. Starts right back up. Idles rough for 10-20 seconds and then settles down and runs fine the rest of the trip. This happens to her twice.


This morning - I'm driving it to work and it does the exact same thing. Sitting at a light, starts to idle real rough and seems like it wants to die but doesn't completely die this time. 10-20 seconds later it's all fine. Drives like a champ the rest of the way to work.


I love this Jeep. Easiest thing I've ever owned to work on and seems to be pretty bullet proof. My wife, on the other hand, is getting fed up with it. She doesn't trust it.


Any ideas? From my research it seems like it would point to one of 4 things: crankshaft sensor (which I replaced); plugs/distributor/coil/wiring (which I replaced); camshaft sensor (which I haven't replaced); or the loose/long screws in the PCM thing (I have not replaced but when I wiggle the wires to the PCM with it running it does not cause it to stall/die).


Thanks again for your help. Hoping to get this back to a reliable state. Again, I seem to notice it's only in hot weather (which we have a lot of) but I could be wrong...

 

My 96 ZJ has the 5.2 Did something similar a few months back. Was sitting at a light with AC on, started idling rough and wanted to die. Volt gauge was below 9. Thought it was battery or maybe alternator, but one battery cable was loose, not making good connection. Cleaned and tightened them up. Been fine since.

 

There's 2 other things that come to mind. Clean your IAC (idle air control) and check the resistance of the IAT (intake air temperature) sensor. At 77*F, the resistance should read between 9.1K ohms and 10.8K ohms.

 

My wife's 98 GC Limited was doing this exact thing. Earlier today, on a 3 mile trip, I had it stall 4 times on me. Pulled a P0108 and a P1297 error code. Replaced MAP sensor. Drove it for about 11 miles without any issues. Will see how it goes.

 

Check the simplistics. The little hose running to your map sensor, make sure its on tight. Map sensor itself. Test the tps with volt meter and math equation. Clean iac, and throttle body. Clean/check grounds for tightness. Same with baterry related parts. Egr diaghram working properly. Check plugs making sure not fouled up already and gapped properly. Clean every electrical connection. My bet is the map sensor, or some vacuum leak. Sorry for the rant. Best of luck. And yes, my xj was bought cheap with intent to sell.the more I worked on it the more i loved it, now I have two jeeps, almost had three. Can u pull codes with the key 🔑 trick?