00 XJ - Does this sound like the camshaft sensor?

I put in new plugs a couple months ago, installed a new CPS about 3 weeks ago and reset the computer. Last week I pulled out of my neighborhood, got up to 35 and it cut off. I've also had some random misfires and multiple times it's felt like it lost a whole cylinder it was running so rough. Cutting the engine off and restarting it temporarily cures everything.

Here's the codes I've got if you guys have any more ideas.

P1391 - Intermittent Loss of CMP or CKP
P0351 - Ignition Coil 1 Control Circuit
P0353 - Ignition Coil 3 Control Circuit

Is this more likely to be the camshaft sensor or is my coil pack failing?

While there is a possibility that the Camshaft Position Sensor is the problem you need to do some testing to verify it is. Do a search for a post by TimMN who posted a test procedure for the CPS and CKPS.
This will assist you in verifying which part is going bad.

CharlesS said:

While there is a possibility that the Camshaft Position Sensor is the problem you need to do some testing to verify it is. Do a search for a post by TimMN who posted a test procedure for the CPS and CKPS.
This will assist you in verifying which part is going bad.

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I'd recommend pulling the cam position sensor and inspecting the teeth on its drive gear. Apparently there's been a rash of problems with them breaking teeth off (mainly in TJs), but at least one late-model XJ has been affected: mine. It crapped out 180 miles East of Los Angeles as I was driving out to Virginia back in 2008. That was three days in Kingman, Arizona waiting for parts to arrive from (amusingly enough) L.A.

Note that this was in a 135,000-mile 2000 XJ that had never been overheated or neglected in my ownership. Oil was changed pretty much on the dot at 3,000 mile intervals with Castrol GTX High Mileage since I acquired it with 72,000 on the odometer.

Apologies for the lousy oversized images - resizing them resulted in loss of what little detail was there to begin with, so it's what we're stuck with.

Wouldn't damaged teeth make it run poorly all the time?

Two years ago the distributor shaft bushing went bad at 103K miles; this caused the curved trigger plate to grind against the cam position sensor shorting out the 5V source voltage.
Towed the Jeep home to troubleshoot and a friend that is a Jeep Dealership Tech stopped by to give me a hand...
His response when we found this was... "That's a new one for me"!!
We replaced the distributor which came with a new C(K)PS and the problem was solved.
The broken tooth on the distributor gear is a new one for me... Almost looks as though some debris was caught between them as they were spinning....
Might be more going on than just a broken distributor gear tooth.

Kevin108 said:

Wouldn't damaged teeth make it run poorly all the time?

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It would - but this was a very sudden failure. 75mph on the freeway and it just went; there were no prior indications of it going out. The reason I bring it up, though, is that yours may be losing teeth gradually - basically, a different failure mode to mine, and one which may cause it to be intermittent or not always noticeable under normal running.

I'm not very clued-in as to what symptoms the TJ guys are experiencing when theirs die, but my understanding is that it's a gradual process of increasingly-worse running followed by eventual total failure similar to what I experienced.

FWIW, I double-checked the mileage recorded on the repair bill from when this happened, and it looks like it was more like 141,000.

CharlesS said:

Two years ago the distributor shaft bushing went bad at 103K miles; this caused the curved trigger plate to grind against the cam position sensor shorting out the 5V source voltage.
Towed the Jeep home to troubleshoot and a friend that is a Jeep Dealership Tech stopped by to give me a hand...
His response when we found this was... "That's a new one for me"!!

Click to expand...

That's almost exactly what the mechanic at the Kingman dealership told me - it was something to the effect of, "in 17 years of working on 4.0s, this is only the second time I've ever seen this happen."

I'll try to get some more info out of my friend with the TJ who has been running up against this later. According to him, the the CKPS design was revised a number of times after the XJ went out of production, and poor oiling of the gear driveshaft is believed to be the culprit. I should point out, though, that this is pretty much the extent of what I know about the problem at this point, but it is apparently becoming more common with midlife TJs as they age.

New part, same old problems. I thought I'd provide some more information as well.

New starter, plugs, new battery, new crankshaft position sensor, new camshaft position sensor.

It usually takes 3 tries to start. Occasionally it sort of backfires on a failed start and blows off the front-most vacuum line on the drivers side of the engine.

Current codes are:

1391 - Intermittent loss of CMP or CKP
0351 - Ignition Coil A primary/secondary circuit
0352 - Ignition Coil B primary/secondary circuit
0353 - Ignition Coil C primary/secondary circuit

The hard start was a new symptom with the new camshaft position sensor. Additional symptoms are occasional rough idle, going into limp mode and running so rough it feels like it's dropped an entire cylinder.

Where did you get the new crankshaft position sensor, new camshaft position sensor ?

The best ones are from the dealership, NAPA is OK, everything else is crap.

Did you replace the cam sensor and the drive and index it correctly?

I just realized you were on both forums, Tim.

I don't think there's any indexing my cam sensor. It has two screws that go through it and that seems to be it. Or am I missing something?

If you replace the drive, which is seen damaged in the images above it needs to be indexed. The sensor itself does fail on occasion, but the drive usually fails first.

From a member of my Jeep club, who is a professional mechanic employed at a local Heep stealership:

jeeptech said:

If it has a big wiring harness that goes around the back of the valve cover, check to make sure it has not rubbed through and shorting to ground around the back of the v/cover. Usually right there on the head bolt. If that's ok I'd put a coil rail on it.

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I will pull and check the drive before I install a new coil rail. What is the procedure for indexing?

http://motorage.search-autoparts.co...estandard//motorage/292005/169830/article.pdf

Basically you need to remove the coil rail, at least spark plug #1 and the drive.
1) find TDC on the compression stroke of cylinder #1. Rotate the engine until you feel compression on #1 with your finger. Or air hissing past it. You are on the compression stroke.
2)Rotate the crank until you find TDC, 0 on the timing cover. If you go past, rotate it back quite a bit and try again.
3) Once you find TDC, put a tooth pick in the drive through the hole in the body and the hole in the window.
4) With the hole for the sensor pointing toward the rear install the drive and bolt down. You may need to rotate the oil pump to get it to line up with the drive.

Yes, that wiring harness can cause a problem, but that is usually found on ZJs, not XJs.

Talyn said:

http://motorage.search-autoparts.co...estandard//motorage/292005/169830/article.pdf

Basically you need to remove the coil rail, at least spark plug #1 and the drive.
1) find TDC on the compression stroke of cylinder #1. Rotate the engine until you feel compression on #1 with your finger. Or air hissing past it. You are on the compression stroke.
2)Rotate the crank until you find TDC, 0 on the timing cover. If you go past, rotate it back quite a bit and try again.
3) Once you find TDC, put a tooth pick in the drive through the hole in the body and the hole in the window.
4) With the hole for the sensor pointing toward the rear install the drive and bolt down. You may need to rotate the oil pump to get it to line up with the drive.

Yes, that wiring harness can cause a problem, but that is usually found on ZJs, not XJs.

Click to expand...

Hah! Great minds think alike!

The most difficult part of this for a newb is finding TDC on the compression stroke.

1) a) As I suggested you can remove the #1 spark plug(its easier to turn the engine over if all plugs are removed). Cover spark plug hole on #1 until you feel/hear air being pushed out the hole. You are then on the compression stroke. b)Assuming your harmonic balancer hasn't slipped you can use the timing marks on the cover. Rotate the engine over until the mark on the balancer is aligned with 0. Do it slowly so you don't pass 0. If you do, rotate the engine back 20* and try again. Do not back up only 1 degree or so to align.

2) You can pull the valve cover. When you see the intake valve close (its the second rocker from the front) you will be on the compression stroke. Follow the directions from b1 after that.

3) Using a compression gauge in the #1 spark plug hole, rotate the engine over until you see compression. Follow the directions from b1 after that.

The hole for the sensor doesn't have to point 100% toward the rear, just in the general direction. Its more based on the wiring harness layout than anything else. You could have it facing forward and it would still work, but the wiring harness may not stretch that far to plug in.


If it doesn't start after this you are most likely 180* out at which point you have to go back and fine TDC again.

I didn't check back here before I got the part. New coil rail, same problems.

I have a new clue, however. Driving around with the scanner plugged up, I've noticed that on the trips I don't have any problems, the scanner never resets. On trips when I have problems, the scanner reconnects itself frequently. Is it possible the whole computer is losing touch with the sensors and causing faulty codes?

The coil rail and the plug I could do blindfolded. I've never had to find TDC on something before but it sounds easy enough. Pulling the valve cover isn't a bad idea either as (like every 4.0) it could use a new gasket.

I'll probably go to my parents' place to do all of this as I'm sure Dad has a compression gauge and that would let me check the engine over anyway while we had the gauge out, coil rail off and spark plug socket handy. That plus having somebody on tap with over 50 years experience as a professional mechanic definitely won't hurt.

And no, the wiring harness is nowhere near long enough to install the cam sensor 180° off.

Thanks for all the help guys. I've definitely got some things to check out now. Also from some deeper searching I'm finding other people with this problem that removed and reinstalled the ECM with good results.

Talyn said:

The most difficult part of this for a newb is finding TDC on the compression stroke.

1) a) As I suggested you can remove the #1 spark plug(its easier to turn the engine over if all plugs are removed). Cover spark plug hole on #1 until you feel/hear air being pushed out the hole. You are then on the compression stroke. b)Assuming your harmonic balancer hasn't slipped you can use the timing marks on the cover. Rotate the engine over until the mark on the balancer is aligned with 0. Do it slowly so you don't pass 0. If you do, rotate the engine back 20* and try again. Do not back up only 1 degree or so to align.

2) You can pull the valve cover. When you see the intake valve close (its the second rocker from the front) you will be on the compression stroke. Follow the directions from b1 after that.

3) Using a compression gauge in the #1 spark plug hole, rotate the engine over until you see compression. Follow the directions from b1 after that.

The hole for the sensor doesn't have to point 100% toward the rear, just in the general direction. Its more based on the wiring harness layout than anything else. You could have it facing forward and it would still work, but the wiring harness may not stretch that far to plug in.


If it doesn't start after this you are most likely 180* out at which point you have to go back and fine TDC again.

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They're not talking about the cmp being physically mounted 180* off, but that the indexing of the shutter window being 180* off if you installed at the end of the exhaust stroke instead of the intake stroke(the crank rotates 2x for every 1x the cam rotates, so the crank could be 360* off and the shutter 180*).

I just want to throw this out there before I start snatching out parts:

My issues are completely inconsistent right now. Sometimes it starts on the first crank, sometimes it takes multiple tries. Sometimes I have problem-free rides. Sometimes it misses and falls into limp mode or cuts off. Nothing happens every time.