High Idle after lift - JeepForum.com
 
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post #1 of 5 Old 03-11-2011, 07:51 PM Thread Starter
1998JeepXJ
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High Idle after lift

Hi, I just installed a 3 in IRO lift kit with 31's. After finishing the install, I started my jeep up and it had a very high idle, I drove it around for awhile hoping that it might go away, but no luck. Any suggestions? Could it be since I raised and lowered it so many times on a 2 post that the ECM is freaking out? maybe I messed something up in the install, I'm unsure, but any ideas would be helpful. thanks.

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post #2 of 5 Old 03-11-2011, 07:55 PM
CJ7-Tim
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High idle is either a manifold vacuum leak, a Throttle Position Sensor problem, or a Idle Air Controller problem. Inspect the vacuum hose and intake manifold for any loose hoses or leaks, test the TPS. Clean the idle air controller and housing.

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post #3 of 5 Old 03-12-2011, 02:10 AM Thread Starter
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Thanks, Ill check the hoses and go ahead and clean that tommorow if a leaks not the issue. Hopefully ill be able to fix it. I think it might have something to do with the throttle, it will accelerate to 30 mph over about 30 seconds without hitting the gas peddle.
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post #4 of 5 Old 03-12-2011, 02:26 AM
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Quote:
Originally Posted by 1998JeepXJ View Post
.... it might have something to do with the throttle, it will accelerate to 30 mph over about 30 seconds without hitting the gas peddle.
That is a very important symptom and it changes what to look for.

Then you need to test the Throttle Position Sensor ASAP.

TPS TEST

You should have 5 volts going into the Throttle Position Sensor (TPS). It is best to use an analog meter (not digital) to see if the transition from idle to WOT is smooth with no dead spots. With your meter set for volts, put the black probe on a good ground like your negative battery terminal. With the key on, engine not running, test with the red probe of your meter (install a paper clip into the back of the plug of the TPS) to see which wire has the 5 volts. At idle, TPS output voltage should be greater than .26 volts but less than .95 volts. Move the throttle and look for smooth meter response up to the 4.49 at WOT. The other wire will be the ground and should show no voltage.

Perform the test procedure again and wiggle and/or tap on the TPS while you watch the meter. If you notice any flat spots or abrupt changes in the meter readings, replace the TPS.


The TPS is sensitive to heat, moisture, and vibration, leading to the failure of some units. The sensor is a sealed unit and cannot be repaired only replaced. A TPS may fail gradually leading to a number of symptoms which can include one or more of the following:

-Poor idle control: The TPS is used by the ECU to determine if the throttle is closed and the car should be using the Idle Air Control Valve exclusively for idle control. A fault TPS sensor can confuse the ECU causing the idle to be erratic or "hunting".

- High Idle Speed: The TPS may report faulty values causing the engine idle speed to be increased above normal. This is normally found in conjunction with a slow engine return to idle speed symptom.

-Slow engine return to idle: A failing TPS can report the minimum throttle position values incorrectly which can stop the engine entering idle mode when the throttle is closed. Normally when the throttle is closed the engine fuel injectors will be deactivated until a defined engine RPM speed is reached and the engine brought smoothly to idle speed. When failing a TPS will not report the throttle closed and fueling will continue causing the engine to return to idle very slowly.

.

A recent Gallup public opinion poll shows the NRA, at 58% approval, has a higher approval rating than either Hillary Clinton or Barack Obama.

Progressive Liberalism: Bringing you new Healthcare ideas so wonderful, they have to include mandatory participation ...

Originally Posted by Ronald W. Reagan: Government is not the solution to our problems; Government is the problem.
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post #5 of 5 Old 03-12-2011, 07:32 AM
cbordea
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we were doing some work on my sons jeep and knocked a small vaccum line off the manifold as mentioned earlier. It idled high and the other key was the cruise wouldn't work. We plugged it back in and voila!

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