cam and crank position senser?

[mrrandyz]

Does anyone know, what are the symptoms for a bad cam position senser? or crank postion senser? Could either of them make my '01 cherokee act like the timing is off intermitantely?

[lilwhitelude]

Either one of them can cause a misfire condition. If it has the check engine light on, get it scanned. Even if its not on, It should show a history code or a hard code if it has misfired though. If you crank or cam sensor are intermittently not working, It may show a cam/crank correlation code. If I know a crank or cam sensor is out, I will go ahead and replace both. Just to be on the safe side.

[fredjacksonsan]

Crankshaft Position Sensor: rough running, odd shifting for auto trans, dies on the road then starts back up a couple minutes later, hard starting and occasional no start.

[mrrandyz]

Thanks for the replies! My '01 cherokee showed a multiple cylinder misfire and some individual misfire codes. It only idles rough for the first 30 seconds after I start it when the engine is already quite warm. Another thing it has done for me twice now, when stopped at a stop sign, it will not start out in first unless I shift it to manually into low. After I shift it into low and put it back into drive, it shifts alright again. Do you think it could be either of these sensers? How much do the cost normally?

[lilwhitelude]

Does it have any other codes other than multiple cylinder misfire? And which cylinders is it missing on. Some of them or all of them? For the crank and cam sensors, I would take it to a shop that has a lab scope and they can check the functions of the sensors while cranking the vehicle. . Most descent shops have a lab scope of some sort. If they don't, I wouldn't let them work on my car. If you have a good book on the car, it will tell you the specifications of the sensors and should tell you how to test them with a ohm meter or a graphing meter of some sort. If its been a while since you had a tune up, Id definitely start with that though. hope this helps some

[lilwhitelude]

I just remembered that those Cherokees have a one piece coil over plug coil pack. I remember back when I was working for dodge, we had to replace a bunch of those because they would cause a random misfire. Just a thought, but I'd check the voltage and signals going to the coil pack. if the signal isn't present while cranking the crank or cam sensor could be causing a problem, but if they are getting correct signal, than the coil pack is failing. We always recommended replacing the coil packs on these things as a tune up item. about 100,000, then replace. Just another thing to check, hope it helps.

[mrrandyz]

Thanks again for the replies! There were no other codes on the computer. I checked both the rail with the coil packs on and the crankshaft position senser's ohm readings; they both checked out within tolerances. Would you still change the coil rail? The Jeep is almost at 100K miles.

[lilwhitelude]

I wouldn't change the coil rail until after you figure out what is causing the other problems. If you checked the sensors and they ohm out, don't replace them yet. It is possible that you have a fuel pressure issue at high temps, could be vapor locking somewhere close to the engine. Ive seen fuel injectors vapor lock, but its usually caused by high underhood temps with a somewhat week fan in the deep south. Shouldn't have that issue this time of year unless your fan really weak, and you are in bumper to bumper traffic.
Your fuel rail may also be losing its prime while sitting. You need to check fuel pressure right after you shut it down while the engine is warmed up to check this accurately.

[mrrandyz]

Thanks! I'll give that a try. The one thing I didn't tell you is that this is a mail jeep, and it only does the rough idle on the mail route (late in the route and after I have shut it down). I have tried wrapping the injectors with heat wrap, and it didn't make a difference. It used to do it only with the 10% ethanal (spelling?) gas, so I just used pure gas. But now it's doing it with the pure gas as well.

[travtug321]

I have a 96 jeep to and it is also mail vehicle. I had to replace the crankshaft sensor about two week ago. It died out on the route and would not restart. It also blown the fuse under the hood 30amp it is the auto shutdown relay fuse. I had two drop the driveshaft to reach the crankshaft sensor on top of the bellhousing. However, I still have the same promblem you do. Mine seems to fall on it face for about 1 minute after restart then will run fine for the rest of the time. I had mine put on a computer it says that it is misfiring on cyc. 1 and 2 while it is run rough then it is fine firing on all cyc. It has not giving me any misfire codes just the downstream o2 sensor. Still does not explain the misfire. I hope this help you a little. I wish I could figure mine out to. GOOD LUCK.

[bigdoffroad]

I have a 2001 4.0 XJ with all the same issues.After running awhile and shut it down.After restarting runs rough,acts like it has a revlimitter set at 2700rpm and cuts back when it downshifts.Have replaced Coilpack,Crankshaft and Camshaft positioning sensers.After driving awhile and shutting engine down when starting back up still have same problem.Also happens while sitting long times in rush hour traffic.CEL starts flashing and starts running rough.If I'm going 55-60mph can put it in Neutral,turn engine off,let coast a few seconds,start back up and it may run fine.Any answers?