Jeeps-R-Us

Recently picked up this '97 GC 4.0L/auto, and got it for a good price because the previous owners were having stalling issues with it. I reveived receipts for past work that had been done including new crank sensor, new O2 sensor, new starter, alternator, and had the head pulled and resurfaced and valve seals and seats replaced because of low compression on a cylinder. We bought it for $775 and had no problems initially. However since then we've been experiencing misfires, idle issues, and stalling. It even backfired once going down the highway at 60mph, it stalled, and then restarted and backfired. I've been trying to track down the issue and have replaced the IAC valve, TPS, Pickup coil, and Ignition coil so far. The information center display in the Jeep started reading Coolant Sensor Bad, so I replaced the one at the front of the motor by the upper hose, and the one in the overflow tank. Most of the time it doesn't show a check engine light, only on occasion. Was hoping for some insight on the problem. Thanks

dave1123

Had a 97 ZJ. Forget about the coolant sensor warning. It didn't mean a thing on mine. The intermittant misfire may be an injector going bad, or a bad connection on one. Check the wiring harness where it goes across the back of the motor for cuts or chaffing. Also check the plugs where they fit on to the injectors themselves. Something may have been damaged when redoing the head.

You might also check the terminal strip on the PCM to make sure it's not loose. Sometimes the solder joints crack where the cable is attached to the PCM.

Sounds like you've already replaced the normal problem items.

Jeeps-R-Us

PCM was next on my list of things, I'm going to try and tackle it this weekend. Checking solder on connections and cleaning contacts and applying dielectric grease to them. I'm gonna go ahead and clean the connections on the crankshaft sensor, IAC, and TPS too and grease them while I'm at it.

dave1123

When checking the PCM, pay special attention to the contact strip for the cable. It often cracks because of vibration and cable flex.

Jeeps-R-Us

Pulled the PCM last Sunday. Soldered every contact, and hasn't died since. Knock on wood, hope that solves it.