Need help! Have a 96 Cherokee with the I6 4.0L. It has a very rough idle. Will sputter at idle and when you give it gas it gets worse, will eventually die. When driving with this problem it will jolt really bad and when pressing on the accelerator nothing will happen. It feels like it isn't getting any fuel. Sometimes I get a code for the crankshaft sensor but I have already changed that. I have changed the fuel pump, TPS, IAC, had the injectors flushed and tested, changed plugs and wires, new dist. cap and rotor. Today I noticed that if I turn on the AC to high the problem would go away. As soon as I turn off the AC it would come back. Any suggestions would be great!

 

Experiencing the same on my 90. Curious if anyone has a solution.

 

If it consistently smoothes out the idle with the AC on max then it sounds like you have a very strange wiring problem. Check the engine and cabin ground straps (block to firewall, block to passenger side fender and under the dash on the driver's side if I remember correctly).

 

I've been told that it could be a wiring problem with the crank sensor. When the AC is turned on it puts more load on the engine and allows the sensor to pick up the crankshaft causing it to run better. I did some trouble shooting and have found a short either in the crank sensor harness or the connection itself. I'll start my search later this week. Hopefully that fixes it. Let you know

 

Have you checked for vacuum leaks? I found a couple of rotted out elbows after I bought mine. Replaced them and haven't had a problem or thrown that code since. Be sure to check the one's under the vehilce before the fuel tank. That one took me a while to find and it was totally by accident.

 

x2 on vacuum leaks

 

Was on my way home yesterday and the jeep was acting up more than usual. Not even the A/C would help. Then I got a battery light. Went straight to parts store to get it checked. Battery was fine but the alternator was not sending out a good reading. I went home and put the new one in. Haven't had a problem sense. Also found that one of the nuts on the alternator mount bolt was gone causing it to be a little loose. Was probably putting out just enough to charge battery and keep the the engine running but not enough to run the electrical system to 100%. Can't believe I spent all that money on new parts and it turned out to be the alternator! Thanks for all the help

 

Good-info.

Thanks for the follow up post so we can all learn from the issue.

 

while at it.....check inside your battery cable winding for corrosion...if the copper is green, then you are going to have bad continuity = bad electrical supply.....jeeps hate anything less than 13-13.5V!