TJ 2000 engine RPMs doesn,t return to idle - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 11-01-2002, 10:51 AM Thread Starter
 
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TJ 2000 engine RPMs doesn,t return to idle

The cold weather is back and so is my problem I posted last spring and got no answer.

At 30000 KMs they replaced the valve seats and since then the engine would not return to idle rpms when you shift between any gear. This occurs mainly on a cold morning from a cold engine startup.

They did change the gaskets between the exhaust and intake mainfold.

Question: Can it be a cold engineor warpped iron vaccum leak that may seal itself as the engine warms up?????????????????????

It difficult to explain this to a services tech if he hasn't experience this problem.


Thanks

Doug in ottawa

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post #2 of (permalink) Old 11-01-2002, 11:26 AM
farfrum
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Re: TJ 2000 engine RPMs doesn,t return to idle

I had a problem with my transmission which would only act-up in cold weather, I waited for the coldest day of the year, and left it overnight at the dealership. I walked in with the keys in the morning and got them to take it for a test drive, they finally found the problem after six previous visits. I just heard you where getting snow in Ontario, anywhere near you? A big hello from Nova Scotia, and good luck with your problem.
post #3 of (permalink) Old 11-01-2002, 11:56 AM
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Re: TJ 2000 engine RPMs doesn,t return to idle

1. Have you checked the Idle Air Control Motor?
a. Pull it (it's loacated on the Throttle Body.).
b. Use Spray Carb cleaner to clean it and the hole in the TB it mates into.
2. Pull the Battery Negative cable.
3. Let the computer -re-train itself.
4. Use Propane, or water, or carb spray and look for a vacuum leak around the intake manifold and throttle body.
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post #4 of (permalink) Old 11-01-2002, 12:24 PM Thread Starter
 
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Re: TJ 2000 engine RPMs doesn,t return to idle

Have you checked the Idle Air Control Motor?
a. Pull it (it's loacated on the Throttle Body.).
b. Use Spray Carb cleaner to clean it and the hole in the TB it mates into.
2. Pull the Battery Negative cable.
3. Let the computer -re-train itself.
4. Use Propane, or water, or carb spray and look for a vacuum leak a round the intake manifold and throttle body.

I have replaced IAC and cleaned and inspected all that I can see.. and resetting computer make no differents.


Thank for the info


Doug in ottawa
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post #5 of (permalink) Old 11-17-2002, 09:08 PM
mib4840
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Re: TJ 2000 engine RPMs doesn,t return to idle

I just took my 2000 4.0 Wrangler into Jeep for what sounds like the same problem. Jeep replaced the throtle position sensor and it corrected the problem. Good luck!
post #6 of (permalink) Old 11-17-2002, 09:10 PM
mib4840
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Re: TJ 2000 engine RPMs doesn,t return to idle

Disregard that last reply I just noticed the date on your post. Hope you got it fixed.
post #7 of (permalink) Old 11-17-2002, 09:40 PM
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Re: TJ 2000 engine RPMs doesn,t return to idle

Flaky IAT (Intake Air Temp) sensor, maybe??

I don't know much about TJ's, but since it's a 2000-model vehicle I am going to assume that the injection system uses a mass air meter (MAF). Most mass air meters are hot-wire type sensors that measure the amount of current needed to keep a piece of wire at a certain temperature; as air flows across the wire, the wire is cooled, and more current is required to heat the wire. The more air, the greater the cooling, and the greater the current.

If there is something flaky in the MAF, the computer may think that the motor is drawing more air than it really is (cold air temps would obviously increase the cooling effect of the air flowing across the hot wire in the MAF) and use the IAC to adjust the throttle position to where everything makes sense (to the computer, anyhow).

As someone else suggested, perhaps the ticket is to make sure that the service tech sees the Jeep when it is stone cold. What I have seen people do before is park a car right outside the dealer's service drive at night, then get a friend to take 'em home... and get a ride to the dealer in the morning (where their car has sat for several hours since they dropped it off). Walk into the service area, grab a service writer by his ear, and drag him out to the Jeep, start it, show him the problem, and tell him to fix it.

Good luck.
post #8 of (permalink) Old 11-17-2002, 11:15 PM
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Re: TJ 2000 engine RPMs doesn,t return to idle

Water? LEVE you must be using river water, since yours must
burn.

False Air - air sneaking into the system AFTER the MAF,
Mass Air Flow Sensor.
Check the ducting between it and the throttle body. Any extra
air sneaking in can cause the fast idle, especially during
cold operation when the ECM is giving extra fuel.
Make sure all the ducts are sealed properly.
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