The cam sensor is built into the distributors on older Mopar 4.0l EFI Jeeps that have one coil and usually give very little trouble. On later 4.0's with coil on plug ignition, the cam sensor is in the oil pump drive that fits into the block where the distributor used to be. It is VERY common for the oil pump drive shaft to start to seize in the bore from lack of lube! When this happens, and you get lucky, all that happens is that the drive spins and throws off the cam sensor sync enough that the engine stalls. If you are not lucky, the drive and/or driven gear/s break and you end up having to replace the cam and the oil pump drive assy.

You can usually see the witness marks where the hold down clamp used to be, and shiny metal where it spun, usually about 1/4" long. Most times, it spins enough that the engine won't run. Sometimes you will hear a high pitched squeek from it as it starts to seize.

The problem usually occurs on 1999 and 2000 models, but occasionally occurs on later 4.0ls too. The latest superceded oil pump drive is an improvement on the old one.

If the drive has not completely seized up, you can disassemble the oil pump drive and smooth out and grease the shaft. You might even add a grease fitting on the side of it between the bushings for occasional re-lubing.

From the factory, when the cam sync was first adjusted during assembly, they set the setting at around 10*, which is the max limit! If you reset the sync to the recommended "0", the engine usually idles noticably smoother. The cam sync setting has no effect on the timing. The PCM knows where the cam sensor signal is supposed to be in relation to the crank sensor input. Moving it only makes the PCM compensate (hense the +/- reading you see with the scan tool). The only way to truly adjust the ignition timing would be with a change in programming (Chip, Flash Update, etc.) or with a change in physical position of the crank sensor.