hesermon

1997 Gr. Cherokee 4.0 - all the classic symptoms. Random stalling, sometimes will start right back up, sometimes has to sit for 5 to 15 minutes. Once it starts it may run perfectly for 2 days or start backfiring, bucking, and dying within 2 minutes. Vehicle has has an engine transplant from a 2000 Gr. Cherokee (had same exact symptoms with old engine) ALSO, sometime alternator will charge at 14 volts then drop to 0, turn the key off then right back on, it starts charging again. Sometimes for hours, sometimes for seconds. Only code is P0351-Ignition Coil #1 primary circuit.
Tried so far, wiggling the PCM connectors (actually works sometimes), used PCM from junkyard (found one that had a rebuild date on it from 8/2011), new tps, new cps, new coil. Tried removing the screws from the PCM cover (read on a forum somewhere). Based on the size of the fireball that blew out the muffler, I don't think fuel is the issue, it has to be ignition.

Has anyone found the magic cure for the random stalling that seems to be so common with these vehicles?

CanuckXJ

This sounds like the exact problem I had on my 93 this summer after trying pretty much everything you listed it finally came down to being a dodgy crank position sensor.

hesermon

That seems to be the most common cure. Don't think so in my case, I had the same symptoms before the engine swap (using the sensor that was in my new jy engine) then put in a new cps the other night. So that would mean two bad used sensors and a bad new one right out of the box.
Thanks for the input though!
Hugh

hesermon

Does anyone think maybe the pick up coil in the dist? I'm really running out of ideas. I thought it was fixed when I put on the new TPS, ran great for about 20 miles, I really thought it was fixed when I put on the CPS, ran great for about 40 miles, now I'm getting lower on ideas AND money!

Radi

If things change when you shake the connectors, something's going on in there. That should not happen.
The harness is common to both old and new engines too, no? Dirty plugs or sockets? Abraded insulation? Broken wire somewhere? I'd go over those connectors pin by pin, wire by wire looking for trouble.
The PCM also controls alternator voltage, so that's another indicator not all is well in that area.

Diesel

Exactly what Radi stated, the PCM has an internal voltage regulator.

Also, on the Grand, un-mount the PCM and try to start it. A common problem is the bolt that fastens it shorts it to the body.

hesermon

Sorry if this posts twice, must not have clicked "post" the first time.
The symptoms are exactly the same before and after the engine swap and with a second PCM. The engine is from a 2000 GrCherokee, the only sensor that did not match up was the oil sender was in a different location. I used my intake w/ throttle body. Since none of the sensors were swapped from one engine to the other (and I've replaced the TPS & CPS) I can't see it being anything but the harness or wiring. Is there a known failure or trouble prone area (I.e along the frame or near exhaust) that I can more likely find a problem? The connectors at the PCM have been cleaned, re-cleaned and cleaned again! All pins appear clean and straight. I'm puzzled???????