2001 Other Jeep Models Engine almost stalls when at a stop

GERRYLIAUW

MEMBER
2001 JEEP
6 CYL
2WD
AUTOMATIC
60,000 MILES

I have a 2001 Jeep Grand Cherokee Laredo 4.0L.
The engine (and transmission) runs fine during driving. Only, when I come to a complete stop, the engine goes below 500RPM (almost stalls), and after a second goes back up to the normal 700/800 RPMs. And after that, it runs fine during idling. So the only time when the engine almost stalls for a second is when I come to a complete stop. If I slow down, remove my foot from the accelerator and just let the vehicle roll forward slowly, the engine also runs fine, untill I come to a complete stop.
I already changed the IAC valve, the TPS and the MAP sensor and cleaned the throttle body.

Appreciate your help on what the solution to the problem is and which parts I might need to change!

9 Replies

RACEFAN966

MECHANIC
5,029 POSTS

Ok it sounds like that it may be the TCM the tranmission control module is not giving the signal to unlock the torque converter so it pull the idle down and then it unlocks and all it fine. Have you check for any codes?

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Tuesday, June 22nd, 2010 AT 10:34 AM

GERRYLIAUW

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Thank for your answer.
I was afraid that it had something to do with the transmission.
I've scanned for any error codes, but nothing found.

However, the problem has changed somewhat the past days.
In my first question I stated that when coming to a stop, after the RPM went up again (after almost stalling) the RPM remained stable.

I noted now that while still at a stop and idling (in drive), the RPM goes up and down with intervalls of a couple of seconds with normal RPM, then a couple of seconds goes to 500 RPM (almost stalling), and then goes up again for a couple of seconds.

Can it still be the TCM? If the TCM would have given the signal to unlock the torque converter (hence RPM's go up), would it/could it give a signal again to "lock" again while standing still?
Or given the update, could it be something else?

Would the idle air control valve that I installed eg need adjusting (the instruction that cane with it said that the valve should not exceed 28mm or adjustment would be needed). I did check and it did not exceed 28 mm, but do I still need to adjust?

Appreciate your help

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Wednesday, June 23rd, 2010 AT 2:37 AM

RACEFAN966

MECHANIC
5,029 POSTS

Ok if the your Jeep is surging then that will not be the TCM. It may be the idle air control motor or another sensor telling the computer to change idle. Do you have a digital multi meter? Do you feel comfortable enough running a couple of tests?

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Wednesday, June 23rd, 2010 AT 9:42 AM

GERRYLIAUW

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I have a digital multimeter. Please let me know how I can test the different sensors. Thanks!

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Thursday, June 24th, 2010 AT 2:53 AM

RACEFAN966

MECHANIC
5,029 POSTS

I need to know if you have had the crank sensor checked out? It is in a hard spot at the back side of the engine. Let me know as this is what I would like to check out first as it is a very common problem with chrysler.