Hi guys, first post on this forum. I don't know anything about Jeeps as I'm more of a GM guy, but my girlfriend has one and it sometimes randomly shuts off on her. Her Jeep is a '95 Cherokee 4x4 with the 4.0 I6 in it. She says that when she goes over speed bumps that her Jeep will shut off sometimes. Lights on the dash and radio still work, just the engine needs to be restarted. I've not been in the Jeep when it does this, but I asked her if any check engine lights popped on and she told me none were present. My guess would be a loose connection somewhere, but I have no idea where to begin.

 

I'd start by checking connections at the CPS which is the harness at rear of fuel rail, the coil wire at coil and dist cap.

 

How fast is she going over speeed bumps?

60 MPH?

 

No, she isn't driving wrecklessly or anything like that.

She called me today while I was driving to work. She was going up a hill and it died. She had it in Neutral and was trying to start it back up, but it wouldn't fire up (I could hear it in the background). I told her to put into Park and see if it would start. Sure enough it did. I'll take a look at the crank sensor and see if anything obvious pops out at me.

 

Wouldnt start in neutral, but did in park. I dont know for sure but maybe it could be a failing Neutral safety switch?

It doesnt cost anything to clean one, just a bit of work. Always an option.

http://www.jeepin.com/features/nss/index.asp

 

If it was the NSS, it wouldn't crank in park or neutral.

NSS prevents cranking in anything OTHER than park or neutral.

 

Ok, I finally got to drive it around for myself last night. The whole Park or Neutral thing is a non-issue; it started up in both gear selections. Here is what happens: When ever you let off the gas, the motor dies. It idles just fine, but when you're giving it gas and you let off, the RPM's drop like they should, but they drop all the way down and the motor quits. I can have it in Park or Neutral and give a quick stab at the gas, and it does the same thing, RPM's rise, then fall and the motor dies. It occurs when driving as well. If you're accelerating and you let off the gas, it dies. It feels like an Idle Air Control Valve issue to me. I'm going to replace it and go from there. Still no Check Engine lights.

 

Fixed.

Turned out to be the IACV.

 

Great job of diagnosing and fixing it yourself.
And Welcome to CF.

 

Sometimes cleaning the IACV and it's bore and reseating the connector is all that is needed. Maybe try that before just replacing next time. Those things are pretty spendy to buy especially when you can get a few more months or a year out of the one you have. Ditto on the good Troubleshooting, Dude!!!!!!