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Unread 07-16-2011, 03:46 PM   #1
highmountaingee
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timing is off on my Country 4.0

I have had major problems with my Cherokee 4.0 6 cyl. country for the last month. I have had my car in one of the best shops in Houston and they can't seem to find the problem.

It is running rich and is heating up the manifold red hot. All the common checks have been made they can't resolve it: checked the computer, crank shaft sensor, vacuum hoses, distributor cap/wires/plugs, o2 sensor, map sensor, you name it they checked it. The timing is off and does not idle properly or just run properly. They say it seemed to have "jumped timing", or "idle jumped"They even pulled the trans to see if the fly wheel was messed up and was not sending the proper signal to the Crank sensor, but it seemed fine.

Now as a last resort they want to "trim" the distributor cap to make it adjustable. I'm not sure exactly what they are going to do, but supposedly they can move cap like a GM and adjust the timing that way.

Does anyone out there know what could have happened to my Jeep?

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Unread 07-16-2011, 06:41 PM   #2
Luke94XJ
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You don't have to do any mods to the cap to "adjust" the distributor. You just leave the hold down bolt out and rotate it while running. Just don't take your hand off of it. I doubt that is the problem though. You may have skipped a tooth on your timing chain. Or have a stuck valve.

The red hot manifold is strange though. You may have bad injectors.
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Unread 07-16-2011, 07:32 PM   #3
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Originally Posted by Luke94XJ View Post
You don't have to do any mods to the cap to "adjust" the distributor. You just leave the hold down bolt out and rotate it while running. Just don't take your hand off of it. I doubt that is the problem though. You may have skipped a tooth on your timing chain. Or have a stuck valve.

The red hot manifold is strange though. You may have bad injectors.
do not do this, this will NOT adjust your timing.

the ignition timing on the 4.0 is non-adjustable


turning the distributor only affects fuel synchronization, and is best left alone
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Unread 07-16-2011, 07:36 PM   #4
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Quote:
Originally Posted by highmountaingee View Post
I have had major problems with my Cherokee 4.0 6 cyl. country for the last month. I have had my car in one of the best shops in Houston and they can't seem to find the problem.

It is running rich and is heating up the manifold red hot. All the common checks have been made they can't resolve it: checked the computer, crank shaft sensor, vacuum hoses, distributor cap/wires/plugs, o2 sensor, map sensor, you name it they checked it. The timing is off and does not idle properly or just run properly. They say it seemed to have "jumped timing", or "idle jumped"They even pulled the trans to see if the fly wheel was messed up and was not sending the proper signal to the Crank sensor, but it seemed fine.

Now as a last resort they want to "trim" the distributor cap to make it adjustable. I'm not sure exactly what they are going to do, but supposedly they can move cap like a GM and adjust the timing that way.

Does anyone out there know what could have happened to my Jeep?
are they sure it's a timing problem? have they done compression test? how about making sure the timing chain doesnt have to much slack? (doubtful though) checked out the camshaft position sensor?
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Unread 07-16-2011, 10:41 PM   #5
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Google Jeep Scan Tool Toothpick Test and perform the simple steps to check and/or adjust the base timing.

I would also suggest finding a garage that doesn't hire Morons to be mechanics.
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Unread 07-17-2011, 12:12 AM   #6
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Originally Posted by CJ7-Tim View Post
Google Jeep Scan Tool Toothpick Test and perform the simple steps to check and/or adjust the base timing.

I would also suggest finding a garage that doesn't hire Morons to be mechanics.
thats only good if he has the DIS ignition....and since he doesnt say what year his xj is, he very well could have a 99 and earlier XJ



X2 on the second part though
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Unread 07-17-2011, 04:43 AM   #7
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Thanks for the info. The jeep is a 94, sorry. I did have the head redone also and they said that would not affect the timing. They didn't check compression because they felt that would not affect the car that way. We checked the crank sensor numerous times and even replaced with a jeep original part recently. Thanks for the input. Any more suggestions?
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Unread 07-17-2011, 07:29 AM   #8
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I agree that it's time to take your vehicle to a different shop. Get a fresh set of eyes on it. It is often the ticket to finding root cause.

How have you determined that it is running rich? Exhaust gas analysis will tell that story in a hurry.

As mentioned, base timing is controlled by the computer. Unless the distributor was removed (was it?) or it jumped a tooth (unlikely), this could be something else other than timing.

Seriously, find another shop (with ASE technicians) and let them take a look. The fact that they want to "trim the distributor cap" is a sign that they are in over their head on your problem. That is not likely to be the fix here.

ROOT CAUSE needs to be established methodically, using a testing based strategy.
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Unread 07-17-2011, 08:45 AM   #9
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Have they performed a simple vacuum gauge test to see if your exhaust is restricted, like a clogged catalytic converter?
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Unread 07-17-2011, 11:36 AM   #10
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The Toothpick Test should work on any 1996-2001 OBD-II Cherokee to check or adjust the base timing when the motor is at TDC.

I don't have a 96-98 on hand to physically check for the alignment holes, maybe somebody can look for them and confirm they exist ?
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Unread 07-18-2011, 09:33 AM   #11
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SFRautomotive, I was just saying that if they were going to modify it to "adjust" his timing, that they could simply test it by rotating it. Obviously its not permanent.
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Unread 07-18-2011, 08:16 PM   #12
highmountaingee
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They ruled out a clogged exhaust pipe, Cruiser54. The issue seemed to have started when I had the transmission rebuilt. The shop took it off, rebuilt it and put it back on. Right after that is when it started to get jerky and completely off. Of course, they said that they did nothing to the car. I had everything checked that had to do with the trans. The crank sensor, computer, flywheel, etc. It's a mystery. I'm not kidding when I say this is the best shop in Houston when it comes to car repair. The owner can tell you practically everything about a any car, any year, etc. They have almost every computer, tester, and machine to repair a car. I was pretty confident they could solve the problem, so that's why I'm totally surprised and confused with what is going on with my Jeep. She's had a good run. I have 384k miles on it and it had been running pretty well, until recently. Hope these guys can find the problem.
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Unread 07-18-2011, 08:57 PM   #13
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Originally Posted by Luke94XJ View Post
SFRautomotive, I was just saying that if they were going to modify it to "adjust" his timing, that they could simply test it by rotating it. Obviously its not permanent.
turning the distributor will not adjust ignition timing on a 4.0
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Unread 07-19-2011, 10:08 AM   #14
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Well It will retard and advance spark, That's ignition timing. But Its not meant to be done. Its not permanent, and only checks to see if someone put it in a tooth off.

It doesn't sound like its his problem either, I was just making the point that if they are the best shop in all of Houston they should know that you don't need to modify it to test it.
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Unread 07-19-2011, 12:57 PM   #15
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Originally Posted by Luke94XJ
Well It will retard and advance spark, That's ignition timing. But Its not meant to be done. Its not permanent, and only checks to see if someone put it in a tooth off.

It doesn't sound like its his problem either, I was just making the point that if they are the best shop in all of Houston they should know that you don't need to modify it to test it.
No it won't. The 4.0 does not adjust timing that way. Timing is determined by the crank position sensor. That is what tells it when to fire, adjusting the distributor will make it run like crap and throw off the fuel deliver timing, that is what the cam position sensor is for.
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