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View Full Version : 01 WJ 4.0 Cam Sensor Issue, others have any?



PassRunnerZJ
10-17-2005, 03:05 AM
This is more of question and heads-up for others running the newer 4.0 w/coil packs. Has anyone else with a similar 4.0 had the cam sensor drive unit seize and if so has the replacement unit done it too?

Back ground: About 61k on the odometer. I'm driving North on I-25 (normal +75mph'sh) just past MM 236 and suddenly the WJ looses power after driving over the tranistion bump between old and new roadwork. The engine didn't stop completely, just no power and it won't spin up w/accelerator. I pull over, eventually onto the frontage road for safety and try to start the engine up and it will start after a few cranks, but it dies when I give it gas or after idleing a few seconds. I use the key on three times to pull the codes on the odometer and it reports that all three coil packs are faulty or have failed.

Solution: After checking connections to the cam sensor and coil packs my brother pulls the cam sensor drive--would be a distributor on other vehicles--and finds that the unit seized. We find a Jeep parts delership open in Ft. Collins--why is it that some dealerships think that they shouldn't have their parts dept. open on Saturday?--and they say they have the replacement part for the matching part number on the pulled unit. Upon arriving at the parts dept they hand me a small box with just the cam sensor in it. Of course it doesn't have the drive unit, luckily they had the drive unit too in stock too. We find out that Jeep/Chrysler sells it in two parts now as rarely do both parts fail at the same time... While we were there the service tech/manager came by and said that they see these cases, and the gear teeth sometimes break off and end up in the oil pan, it almost sounds like this happens often.

Upon matching up the position on the new unit to the old unit position, like you would a distributor we installed the new drive and new cam sensor unit. Start the WJ and it acts the same, hmmm... After comparing the old with the new I realized that old unit spun some when it seized and thew the timing off. So doing the logic backwards we moved the new unit counter clockwise close to where the lockdown fingers started digging in on the old unit and the WJ started and runs fine now (actually did the passes with more speed going home than it did on the trip to the front range for the soccer games.)

Hindsight:A few weeks ago the WJ threw a cam sensor error when the wife started it one morning and it acted like it was a bad start. I attributed the bad start to dirty plugs and didn't think much about it as the error didn't show again after pulling the code and the wife drove it without any problems before the trip, but it must have pulled the timing off a bit as I imagine it started spinning the unit. In hindsight even if I would have replaced the cam sensor it wouldn't have prevented the drive unit from seizing, but it was good to remember that it was the initial warning code I received when we were looking for the reason for the I-25 failure. Also, I think that the coil pack codes were caused from the cam sensor being so far off.