91 XJ has been shutting off randomly while driving. It does start back up and run. Figured it was the CPS so I switched it out with an ebay $20 sensor. It starts up and runs but if I let it idle for a couple minutes it will shut off at times (not always) and still shuts off randomly when driving. In short I'm getting the same symptoms with a new crank sensor. Could there be another issue at fault here or should I get an oem crank sensor? I was told that if the cps was bad the jeep wouldn't start at all.

 

I've seen CPS failures on other vehicles where it will fail as it heats up and work again for a while after cooling off. Of course it could also be a wiring or grounding issue.

 

compare the magnetic strength of an oem sensor to an aftermarket and you come up with your own conclusions regarding a $20 ebay sensor...

 

Ebay crank sensors, especially brands you don't recognize, are generally pretty low quality. And that is being nice. I recommend only MOPAR crank sensors purchased from Jeep.

But that being said, your problem could be something else. The ignition coil on the XJ can suffer from "thermal failure" (heat related). If it was my vehicle, I'd run it in the driveway until it fails, then take some quick tests of both primary and secondary resistances of your coil (you'll need a manual and a meter) to see if it might be in play here.

FYI, a crank sensor can fail when hot and when it cools down, can work again. It's not that uncommon actually.

If you find the root cause to be something other than your crank sensor, you'd be better off reinstalling your original crank sensor than your currently installed ebay crank sensor. I'm serious about that.

Have you checked for any stored codes in your computer? Even if the check engine light isn't on, it's something I would recommend.

 

I replaced the cps with an oem and still the same symptoms. It starts up but shuts off randomly. In traffic when it dies I can drop it down to neutral and start it back up. Fuel pressure is good. I did notice a bit of sputtering at times as if the transmission is hard shifting. It never did that before. I did a full tune up about 3 months ago cap, rotor, wires, plugs etc. It ran good until a few days ago and I didn't make any changes its just random. Can it be the ignition coil? Would an ignition coil cause the engine to just shut off like this?

 

THIS ^^^^^^^

My son had is having a problem with his XJ, he told me he needed a crank sensor so I went out and bought one.

The symptoms, all but said crank sensor.

However I pulled codes and turns out it's pointing to the cam sensor in the distributor.

Tomorrow original crank sensor goes in, and also most likely a new distributor since I cannot find the sensor locally by itself.

 

It was the ignition coil. Jeep is running good for now.