KJ question sorry.

[cushdaddy]

I have posted this question on the liberty forum and have gotten no response. Frustrated and annoyed at this thing. Throwing cam sensor code and I have tried 4 different cam sensors. Different pcm and checked timing. It will only start on one of the 4 sensors I have. Unplug cam sensor after start and it runs fine. Must be running off the crank sensor. Throws p0340 code. Could I have 4 bad sensors? I checked the wiring to the PCM and shook the harness and everything was good. If it was a wiring thing, I would expect the same result from one of the other sensors. The Chrysler sensor will not start the jeep. Any ideas would be appreciated. I have a 1998 xj that is my daily driver and it's way better then this frigging kj I am working on. Thanks.

[Ecomike]

LOL, on the 98 XJ. Try starting with it disconnected? To see if perhaps the one sensor is the bad sensor and not the good one, ie there be a wiring issue that is solved by a bad sensor? Just a wild guess as I know nothing about liberty yet, except that my son bought one recently.

[Green Mesa XJ]

What year is the KJ?
I assume it has the 3.7 v6, which I do know a little about.

Far as sensors go unless they are mopar you can get a series of bad sensors. The aftermarket on jeep sensors is 80% cheap Chinese part that have a very high fail rate. Even for xj parts you can get a bad CPS out of the box. One guy here went through several Oreilly brand cps until he found a good one.

I think 2004-5 Chrysler changes the computer to a different style,
2002-04 one style pcm with certain spaced inducter plates setting the timing. 2005 up to 2012 is a different pcm and number of spaces counted for timing.
Unless the motor has been apart or swapped this shouldn't be a issue. Timing is pretty much set in those 3.7, lifetime chains. Only things that fail are the tensioners and plastic guides.

I don't know how the engine kept running after losing the cam sensor. guess it has a limp home mode.

My guess is the sensor is bad like the code says, swapping the sensor from a running 3.7 it might be a way trouble shoot other than that your best bet is find a mopar part. Probably about $30-40, sometimes cheaper on ebay but you have to be careful of bad parts being sold or cheap Chinese parts being sold as mopar under names like "OEM"


Other possibility could be a heavily gunked up engine, unlikely and it would have to be extreme. I'll do some searching see if anything obvious come up. Surprised the KJ board hadn't stepped up more, usually the KJ guys and gals are pretty good about helping




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[Green Mesa XJ]

Ok, that code can be a pain. Easiest fix is bad sensor.
Next is a wiring trouble someplace, then a failure in the PCM. If you've swapped the PCM already it's probably down to wiring or sensor.
Most report mopar sensors fixing the issue. Tons of reports of bad parts from , Vato Zone, advance, O'Reillys . Napa is the next best go to is Mopar is not available.


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[trippled]

How has the timing been verified? If it's like the 4.7, the chains stretch and set cam sensor codes. Another option is shimming the sensor out some. Sometimes they can pick up imperfections in the gear and set false codes (gm offered a shim kit for the crank sensor on the 350s for this).

[Green Mesa XJ]

Might be possible for chain stretching, the 3.7 (2006) I took apart the chains had negligible stretching at something like 150-60k, a f150 5.4 (2005) with nearly 200k the chains were identical side by side with the new chains. Hyundai chains in their v6 (both were 2006) looked good too.
What was worn out in all those engine were the plastic timing guides and the some tensioners were a tad gunked. Which I guess in extreme cases could mis timing it if something slipped.

Of those engines The chain design in the 3.7 is the most complicated to set up, it is three chains instead of one or two. Now that I think about it Hyundai might have a third chain too, still I think the 3.7 was more of a PITA to setup.

The 3.7/4.7 a interference engine so if the timing does slip it's toast.


I hadn't heard of the GM sensor Shem solution.

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[cushdaddy]

Thanks for the replys. The jeep is a 3.7. it had a blown head gasket, so I replaced it. Yes, the timing is a pain. I replaced the chains and the guides while I was at it because the guides had a bunch of wear. I have had the valve covers off to verify the timing about 6 times. The timing chain kit I bought came with new tensioners. It does seem like the chain in the sensor side is not at tight as the driVers side. I am throwing P0340 and P1391. Cam and intermittent cam sensor. The tensioner is hydraulic as it has an oil port on the back. Possibly not tight enough? Thanks.

[Green Mesa XJ]

In that case i am probably wrong and it may be a timing chain issue.

You're using the same cylinder head ? The right side were the sensor goes has the reluctor the PCM reads and those reluctor change when the computers go from JTEC to NGC. Although I doubt it start with the wrong reluctor.

I'd check the tensioner again, I remember them being a PITA to install.


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[cushdaddy]

To check the tensioners I have to pull everything off the front of the engine again. Thats a PITA. The tensioner doesn't explain the 4 different sensors, unless they are in fact all bad except the one. That's where I am at though I guess.

[Ecomike]

I am glad I do not own a JK.

[Green Mesa XJ]

The sensors can be bad out the box. If nothing else had happen and it just quit the sensors would be my guess, new timing chains and tensioners now I don't know.
I'm not sure how sensitive the Cam sensor is to cause a failure. It could still be sensors, but the slack in the chain is worrisome.

Have you tried the forum @ jeepKJ.com?
I went there with question about the 3.7 in our commander, they knew the 3.7 inside and out.

Getting into the really intricate settings I'm not so sure what's normal or acceptable on those motors.

I don't think the 3.7 is a bad design, it's just not a iron head 4.0.


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[cushdaddy]

No kidding. I love the 4.0. even the 4.2. bomb proof. Knock on wood. I'll pull the timing cover and check the tensioners on this next weekend. Hopefully the crank and rods will be back for the other one early this week and I can get the other engine back together for the other one.

[Green Mesa XJ]

When ever the apocalypse actually happens there's going to be a few 4.0 rolling around just cause they refuse to die. Simple design works.

I was so used to the tank 4.0 the delicate 3.7 was a rude awakening, but it's better than other motors out now but not the old straight 6.

Looking at a 3.7 I have in the garage to rebuild someday that tensioner is behind the timing cover with no other good way to get at from what I can see. I wish I knew how much slack was acceptable.








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[Flyfisher]

"it had a blown head gasket, so I replaced it. Yes, the timing is a pain. I replaced the chains and the guides while I was at it because the guides had a bunch of wear. I have had the valve covers off to verify the timing about 6 times. The timing chain kit I bought came with new tensioners."

There's some critical, need-to-know information!

[cushdaddy]

What critical info am I missing? Thanks