Tim9368

Here is the original post, when I had no codes:
https://www.cherokeeforum.com/f5/hel...alling-139285/

Now the CEL is on, and autozone gave me P0351 (ignition coil) and P0108 (MAP or MAF Sensor)

At least I have something to go on here. The little paper they gave me at AZ gives some hints of what might be causing this, but I don't want to throw parts at it. Any suggestions on how to proceed here? Specs for testing these sensors with the multi-meter? As always, thanks to all for your help.

From Twitchy Jeepland,
Sincerely,

-tim

weezer41

Same thing happened on my 98 JGC. I replaced the coil, but the stalling continued. On mine, it appears to be a loose connection where the wiring harness plugs into the computer. And no codes are showing as before.

Tim9368

All the connections have been inspected, cleaned and refreshed. This stuff drives me nuts!

CrazyMacaw

You need to wiggle the PCM connectors and wires while it's running, if it stumbles or stalls then you know the connectors are having a problem. Just looking and cleaning isn't enough. If wiggling the connectors has no effect you might also try tapping the side of the PCM itself with a screwdriver handle or pressing on it's face with you hand looking for the same symptoms to test for a cold solder joints in the PCM. If the connectors are having issues a quick dirty fix is to wrap the connector and the PCM with plastic wire-ties to hold the connector more secure.

I noticed you said you used dielectric grease in your original post, that stuff is an insulator, if you gobbed on too much of it and it got into the connector sockets it could causing intermittent issues as well.

Tim9368

The pressing and wiggling test has been done, and we cannot seem to duplicate the stall. Should I get in there with electrical cleaner and clean off the dielectric grease?

tjwalker

Follow the codes. Always follow the codes. They aren't perfect but they are awfully darn good at pointing you to the offending circuits.

I would start with the P0351. Ignition coil no. 1 Primary Circuit.

Here is a link that explains the code.

http://www.obd-codes.com/p0351

If this were mine, I'd probably start by replacing the ignition coil. They are not that expensive. You aren't running an MSD or Accel coil are you? I've seen a LOT of problems with them. For ignition coils, the 4.0 needs nothing more than an OEM style coil. You gain nothing with an MSD or an Accel coil besides compromised longevity; they just don't hold up.

You really must rule out the coil before moving onto more complex possibilities. But that being said, the computer itself could be the culprit. I've seen reference to it before. Here is a link to a thread that has the same codes as you do.

http://www.moparchat.com/forums/showthread.php?t=88780 Sound familiar?

If you do decide to try a new computer, try to purchase a salvage yard computer. New stuff is prohibitively expensive. A good salvage yard should be able to help you get the correct one, even if it has to be shipped in.

Hope this helps and be sure to keep us updated!

Tim9368

Yes, this sounds familiar! The suspect al along has been the PCM for a number of reasons. I got a quote from a Jeep specialist shop here in Austin to replace the PCM with a 1 year warranty for <$400. That sounds reasonable to me.
>
Before I switch out the coil, one more update: Later today the CEL turned off, but when I went back to AZ, the codes were there, but the Tech could not clear them. I am leaning more and more toward that dang PCM.

Thanks again for your help. I will keep you posted.

-tim

Tim9368

Just Confirmed that the ignition coil is new (got the car from family) Just about all sensors were replaced - no codes were thrown before and the PCM has been the main suspect for a while. I'll keep you posted.

Tim9368

Just got it back from my specialist. Apparently the failed ECM/PCM on 96-98 model Grand Cherokees is fairly common. $500 got a remanufactured unit installed and warranteed for 12 mo/12k miles. I consider that a bargain if in fact this fixes the problem. I will post after a while when I am sure it's fixed.

Thanks again for your help everybody!

-t

Tim9368

All symptoms are gone after several weeks of driving in all types of conditions. Apparently there is a design flaw in the PCM of this particular vintage. The following video gives a good explanation of what happens...


Thanks for the help everybody-

-t