1993 GC Limited - I Miss My Jeep!!

Wow......

I too would be suspecting the junkyard brain. Maybe a 'new' one would be in order.

And FYI, I know that some 258 and apparently some 4.0 engines won't run on bosch plugs. The plugs foul black very quickly and the engine misses like a bugger. When I switch them to Champion plugs they run fine.

I likely mentioned this before, but when you have a missing or broken ground path, the vehicle can steal grounds through things like gas cables and radios and shifters and brake pedals. This normally causes all kinds of seemingly unrelated issues usually computer or sensor related. One main computer ground tag point is usually a bolt into the block near the dipstick. There are a mess of black wires there. Sometimes one gets dropped out when it gets hooked up.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail >

Yeah, it is definitly a suspect. I hope to know either later today or in the next couple of days. Since I have access to a newer one (not new tho), I am hoping that will help resolve things if it's needed.

I have heard that, but have been using the Bosch for a number of years on several of my vehicles and have yet to see this occur, until just now. I'd be in agreement if it weren't for the fact that the other plug brands are also fouling right now in the Jeep.

Yep, went over this near the beginning of this saga. Checked them over several times and found nothing. Although, since I know some of the wiring has been replaced due to damage/shorting in the accident, I keep reminding the mechanics that there still may be something they have yet to locate.

Another concern mentioned to me was that the CPS (Crank Position Sensor) may have a shim issue and or been damaged. I'm not too familiar with how the vehicle can react with a damamged one, but I am hoping this has also been looked at. I've got one mechanic saying his tests show it's bad and a second mechanic saying it's good. Bear in mind, it's already been replaced once, same time as the PCM.

Thanks for the input Mike!

`Casper

I plan to post what the final outcome is so hopefully no one else will ever have to go thru this and glean some useful information from my problems and saga. :)

When the CPS goes bad, the vehicle usually up and dies. The plug and socket for it can and do get dirty though, but again that usually causes a stall. There are no shims on it, it just fits in one spot. People do try to alter it for modified vehicles, but that isn't normal use.

Mike

Casper wrote:

Jeep uses 2 (at least) types of CPS units.

There is the one type that is secured by one bolt, that must be adjusted for clearance with the paper spacer that comes with the new unit..

The other type is secured with 2 bolts and does not require adjustment.

The later is the version on my jeep. I said shim but meant spacer. I know if the spacer isn't right when the replacement is installed, it can completely ruin the new CPS.

Right now we're still testing and tracing as much as possible but coming up empty. We're still leaning towards a mis-matched or mis-programmed PCM.

Anyone ever hear of paint particles from autobody work getting into the sensors and causing problems?

`Casper

Silicone RTV fumes can kill O2 sensors faster than you can blink. They now make the more expensive 'sensor safe' silicone RTV. If you have fresh silicone anywhere near the engine it could cause continuing troubles.

I can't see how paint can get at sensors, but it could interfere with some.

The only CPS's 'I' am familiar with just bolt in. There are no spacers. I haven't seen that many though.

Mike

Casper wrote:

The only sensor that can be affected by gas is the O2 sensor. RTV especially. I'm not sure anything but epoxy based paint would cause problems. Hardly anyone uses epoxy paint anyway.

The rest of them are basically immune or hanging off of vac lines with no exposure.

After swapping to Champions, add a fat ground braid between the body near the battery and a nice big bolt on the engine. If that doesn't do it, maybe the brain and or coil is just too weak to spark.

Mike Romain proclaimed:

Bosch plugs are crap. If you have one of their universal fit, splice in, POS O2 sensors, throw that away too.

Has anyone verified a problem with any of the parts you replaced, or are we using the shotgun approach?

Has the check engine light problem been resolved? If not, you need to start there, since it indicates a problem with the PCM grounds, power feeds or the PCM it's self.

First, MDS doesn't even exist anymore. Second, even if it did, it wouldn't do you any good. You need somebody who knows what he's doing to diagnose it.

As I see it, you have 2 choices.

1) Take it to somebody who knows what he's doing.

2) Go postal.

As I said, the plugs have been replaced 4 times. O2 sensor no, but that's been tested several times.

There have been 3 master mechanics working on this issue. It is currently in the hands of a master tech who specializes in electrical problems and trains techs across the country in troubleshooting.

As I stated, the PCM has been replaced already (once). That resolved the check engine light.

Again, it's been in the hands of three (maybe more) master techs, including one who is a master with the MDS. That was a specific request made to Crysler.

Been there, doing that... at least the best I am told is around here.

Lon hacked up a hairball and the stain left behind looked like this:

Again, the plugs have been replaced four times now and the ground checked more than you have fingers and toes. Also, the PCM has already been replaced once along with the coil. No change.

I'm not paying for any more replacement parts until the master technician can tell me for certain what is the problem.

Yeah, sounds right to me. I've seen how the sensors attach and found the suggestion hard to believe, but it cannot hurt to check and ask if anyone has heard of or run into such a problem.

Sorry about the wording. Spacer, shim, whatever. It's a small piece of paper-like material they use just to install the CPS.

I didn't know there were different ones either, but the two mechanics currently working on it showed me the difference and the one I have. I really wish I had the other one.

I still want to know how one mechanic can say the CPS is bad and the other says it is fine... and they are both using the same diagnostic tools to test them. I am downright suspicious of all dealership mechanics (past bad experiences at dealerships) that he really is just surmising that is the problem from experience, but /shrug. It's been replaced once already. I would think master techs know how to put one in and not damamge it (or anything else).

Truthfully, right now I really don't care about anything except someone fixing it. I've already reached my limit on patience with the pointing fingers and no resolution. Either I get it back working the end of this month, or the insurance company of the guy who hit me is going to have to replace it. Otherwise I am starting by camping out on the insurance co's front lawn with nasty signs and going from there.

Just to clarify things up a bit (I hope)...

For the check engine light problem, the PCM (main computer). Aside from not running the pre-start process, it was preventing voltage from going to the fuel pump.

A smashed connector in lift gate was replaced. The tailgate tamper circuit was spiked by a short to a power circuit which required the replacement of the theft module but the jeep would still not start until the replacement of the PCM.

The crank position sensor (CPS) was replaced (once). I was informed it was found bad during the process of troubleshooting and before replacement of the PCM.

The sparks plugs have been replaced four (4) times now in total for fouling. Bosch plugs were only used once and the jeep only drove about

12-15 miles total on them before being removed. *You can smell fuel after several attempts (cranks) to start.

The ground(s) have been checked by four (4) different mechanics and determined to be fine. Wires starting from battery and continuing till end have been checked and cleaned.

The coil has been replaced when it was thought the spark voltage "might" have been low. No change in problem.

She is still sitting in the shop with several different diagnostic tools wired to her looking for anything leading to the problem.

If you want to know about the mechanic, check this out...

And here is something he designed... So far Jeff appears to me as a very honest guy who is a very knowledgeable master technician and mechanic. He has given me no reason to suspect otherwias and has been both helpful and diligent in working to resolve my jeep's problem(s).

`Casper

I have to agree with Mike. There is nothing in the service manual about any shim or spacer under the CPS. Neither is anything included with a new CPS that looks like that. I have one sitting in front of me. I'm curious about the two, different CPS units the mechanics showed you. My '93 ZJ V-8 was one of the first produced in 1992. It has the 2-bolt type as shown in the service manual. The Mopar No. for this CPS is 1-56026701.

Dick

On the 93 production year there were two (possibly three) different transmissions and two different CPS sensors. 92 1/2 or early 93 production run and the 93. Mine is a mix of 93/4 parts and a pain in the ass to order parts for.

The original on-hole CPS sensor doesn't actually have a hole in so much as it has a slot. On the original sensor there is a cardboard bit glued to the end. You just slide it in till the spacer hits then tighten it down. The spacer then erodes.

They did away with that sensor/spacer sometime in 94 and replaced it with a fixed hole in about the same location as the old sensor was fitted. Guess they improved the sensor or decided the gap was not too critical.

I'm getting the idea that we are discussing the 4.0 engine, and not the V-8.

Dick

Correct. 4.0L inline 6 cylinder.

Not to take anything from your mechanic, but it looks like he's had mostly GM training, and probably has mostly GM experience. You may be better off with somebody who is experienced with the Chrysler systems. Being familiar with a system is a big advantage.

He designed a current probe? Any decent automotive lab scope kit will come with one of those, and they're not $400.

Again, he may be good, but this problem has been going on for quite a while now with no fix in sight.

Does he have a DRB?