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Phantomoak

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Discussion starter · #1 ·
I have been having this problem for a LONG time, and have gone through every google hit I could on this...

I am on the brink of junking the Jeep with only 166k miles :(


I have replaced almost every part, from plugs to the computer (including the normal culprits like the CPS). It has just become worse, to the point that it is undriveable, stalling every minute or so, taking a 2-5 minutes to restart, etc.

I often could throw it into neutral and rev it to ~3000 to keep it running (poorly) until it got over its hickup, but that does not work anymore...




So, today I was seeing if it would idle in the driveway, and it stalled so I started looking around and noticed the Fuel Pump Relay was crazy hot (brand new, changed out this week)...

Does that have anything to do with the problem; is it a symptom of the problem?

Other quirks: Reverse disengages while backing down my moderate incline driveway; revving the engine is the only way to get it to engage again. Maybe there is a short in the electrical system causing both problems? I am just out of ideas.



I am looking at buying a new vehicle this weekend if I cant get it running by the end of the week... I would GLADLY drop $2 or 3 K into this jeep but the no one can even tell me the problem.
 
Okay, so you definitely have a bad ground. Likely a cheap/free fix. Look at where your computer (pass firewall corner) is located, and locate the grounds from that main harness. Those are known to corrode, which can cause the engine to run all ratty, and also cause other issues. In fact, spend a couple hours and check all your grounds. The ground strap from engine to vehicle (braided steel) is also a common issue. Def cause a rough running engine.
 
Discussion starter · #3 ·
Okay, so you definitely have a bad ground. Likely a cheap/free fix. Look at where your computer (pass firewall corner) is located, and locate the grounds from that main harness. Those are known to corrode, which can cause the engine to run all ratty, and also cause other issues. In fact, spend a couple hours and check all your grounds. The ground strap from engine to vehicle (braided steel) is also a common issue. Def cause a rough running engine.
Can you explain where the grounds might be (and be bad) a little more clearly?

I am a turd when it comes to grounds... complete novice
 
Start off my removing your battery terminals so you don't short anything. A steel bristle brush, emory cloth or med-grit sandpaper, brake-kleen and some rags help. Then...

Well, the engine ground strap (braided, flat, steel "belt" w/ ring terminals on each end) SHOULD go from the back of your cyl head to the firewall, I BELIEVE. For the battery, obviously you want your post/terminal to be REALLY clean. DON'T use coca-cola, it'll work but makes a sticky mess. The parts store should have a can of batt terminal cleaner for like $5. Follow the cables from the negative post to the fenderwell, and follow the other one down to either your frame or engine. There is also a ground from the alternator to the engine, that's pretty straightforward.

The PCM, located behind your coolant reservoir (remove this to really get in there easier), has a harness with an 8mm bolt in the center. Remove that and check to make sure there's no contamination or corrosion. You'll see there's like 80 wires going into that harness:eek:. You'll have to just follow the black ones to ground. IDK off top of my head which ones, or where they go, it's a matter of patience. A razor to cut open the wire loom (be careful not to cut wires) and some electrical tape to re-wrap it after you're done are a must.

It's still possible that I'm wrong and that your grounds are fine, I've just seen bad grounds throw a good mechanic "under the bus" so many times...
 
And just to add, if you see any melted wire looming while you're in there, I'd open the loom and inspect the wires. Like around your exhaust manifold, etc. If the loom is melted or covered in lots of greasy buildup, the wires inside could be compromised, cracked, or broken.
 
Actually it IS the PCM causing your problem, the board has poor solder joints from 1993- 1998 on EVERY model Grand Cherokee. The ground for the ignition is controlled electronically from inside that unit. This forum is lacking on repair and replacement of this faulty unit I have seen. I drive a 96 Limited with a faulty PCM and have what they call the "Hose clamp" fix for now. If you know how to solder, open the unit, get the compound off and remove the moard to see the solder side. On another forum there is a diagram of one takenapart showing the solder points that are bad needing fixed. Everyone on that forum that follows this problem has not had any issues since. Cheaper than buying another unit and having it flashed for your Jeep. I did a search on this site for PCM .. nothing .. then I searched STALLING PROBLEM and found several pages of posts I am answering all of them on finally how to fix this. Good luck, if you want the link to the other forum I am a member of for the diagrams and how to fix it yourself and ignore the useless Jeep and Mopar techs let me know I will gladly post it here.
 
Actually it IS the PCM causing your problem, the board has poor solder joints from 1993- 1998 on EVERY model Grand Cherokee. (snip)..if you want the link to the other forum I am a member of for the diagrams and how to fix it yourself and ignore the useless Jeep and Mopar techs let me know I will gladly post it here.
I haven't had said problems yet (knock wood) but I would really like to see the fix on soldering up the PCM you did. I'm sure my old '93 Laredo is good candidate for this hopefully 'future fix'. Thanks!
 
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