Lowrange2

Get it running and try wiggling all the wires that connect to the PCM. See if you can make it die.

Once upon a time I had a bad connection in that big *** PCM plug.

ZJs are bad about this too.

mike96xj

No pattern what so ever, its dies at stop lights, going up hills, drive thrus, idle, rolling down a flat straight road. Completely random. I took it to an auto repair shop for a diagnostics and the heep WOULD NOT die for them. They told they check much unless it dies. The only recommendation they gave me was cat conv.

mike96xj

PCM?

Lowrange2

Since it's not stumbling and dieing we can assume it's not fuel related.

Usually even a IAC or TPS would cause it to stumble or run rough before it dies.

The only thing that should kill it abruptly like the key is being turned off is the CPS, Ignition coil, bad connection in one of those circuits or the PCM.

Lowrange2

PCM/ECU. The computer.

The big *** black box with the big *** wiring harness plugged into it mounted between the airbox and the drivers side fender.

mike96xj

Im assuming thers no way to test it? Better to try a junkyard find?

Lowrange2

No no no. The PCM is probably fine. There could be a bad connection at the PCM somewhere.

Start the Jeep, split the loom back so you have access to all the wires at the PCM, wiggle them all individually and see if it dies when you wiggle one particular wire. If it does, fix the connection.

Probably wouldn't hurt to pull the plug off and make sure it's nice and clean and plug it back in.

Keep in mind there's a bolt through the center of the plug.


Man, I'm almost leaning towards an ignition coil.

It's hard to test intermittent issues without being able to MAKE it die at your command.

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One more thing. Is the Jeep acting EXACTLY like it did before the CPS swap? CPS are known to be bad right out of the box but it's pretty unlikely that it'd still be doing the exact same thing with 2 different CPS's.

mike96xj

Ill have to check the PCM wires when i get home. But yes all the symptoms are the same before and after the CPS swap.

Lowrange2

If you're willing to risk another 35 bucks...

I'd say my next part I'd throw at it would be an ignition coil.

http://shop.advanceautoparts.com/web...034%7CL3*16064

If it don't fix it, make friends with a salesperson and return it.

If you do try that you can just plug in the new one and just lay it in there to see if that helps. You don't need to bolt it down to give it a try.

mike96xj

How do you go about checking the coil for spark? I tried pulling the middle plug of the dist cap connected to the coil and thru and old spark plug in it and nothing.

Lowrange2

As soon as the Jeep dies, hop out, pull a spark plug stick it back in the wire and ground it somewhere and have someone turn the engine over while you watch for spark.

It won't be there but that really doesn't help narrow down the problem.

Though, if you do have spark but it's a weak spark then I'd say your coil is shot.

Or you could just....

Wait till the Jeep dies, turn the key on, pull the wire off of the coil and stick your finger on the stud on the coil. You'll know if it's working.

Or you can do this.

http://autorepair.about.com/od/troub...l-test-ohm.htm

Lowrange2

I'd test the CPS as well just to be sure.

Still sounds like you have bad connection somewhere.

mike96xj

Hard to see but there is a crack along the bottom of the coil near the mounting bolts. Could this be the problem?

mike96xj

Black89

It's hard to say if that would be an issue but it wouldn't hurt to replace it. Also check your connections at the coil as well. I just happened to find this on youtube. It's a 96' but it seems to be common.
I had a coil go bad on my 93' blazer and you could do a resistance check on it. Mine was zero. When it got below 50 degrees it would do nothing, in a heated shop over night it would fire right up. Sounds like yours is either connection related or it's over heating which is usually when they are bad. Cold issues with them is rare.

Black89