2003 Jeep Laredo air idle control valve

Tiny
SACOREY
  • MEMBER
  • 2003 JEEP LAREDO
Engine Performance problem
2003 Jeep Laredo Four Wheel Drive Automatic 110000 miles

Replaced idle contol valve lasted about a week replaced again still no high idle when cold and low idle when hot. Where do I go from here? What other compoants do I have to check?
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Sunday, February 28th, 2010 AT 7:38 AM

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Tiny
CARADIODOC
  • EXPERT
First of all, if the battery was recently disconnected or run dead, the Engine Computer lost its mind and must relearn "minimum throttle" before it will know when it must be in control of idle speed. To do the relearn procedure, you must make the engine meet the conditions at which this will occur. Drive at highway speed with the engine warmed up, then coast for at least seven seconds without touching the brake or gas pedals.

If it's not batery related, you'll need a scanner, a hand-held computer to read the sensor values and idle control "steps". Most aftermarket scanners should do this but I use the Chrysler DRB2 and DRB3. There are 256 "steps" the computer will set the Automatic Idle Speed (AIS) motor to. That's the part you replaced. For a properly running engine, step 32 is a typical step for a normal idle when warmed up. If you find it's around step 50 or higher, the computer is trying to increase engine speed but not getting the desired response. Look for carbon blocking the air passage the AIS sits in. If the steps are 0 or real low, the computer is trying to slow the engine down or it hasn't learned minimum throttle yet.

Also look at the temperature the Coolant Temperature Sensor is reporting. If it is not in line with the ambient air / battery temperature sensor when the engine is cold, the computer will know it can't trust that sensor. It will try to make judgements based on other sensor readings. The results are less than perfect, but the engine will run. Normally a conflict between various sensors during various conditions will be detected by the Engine Computer which will memorize a diagnostic fault code and turn on the Check Engine light.

Caradiodoc

caradiodoc
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Sunday, February 28th, 2010 AT 8:03 AM
Tiny
SACOREY
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Thank you for your help. Have a scann tool can make the idle go up and down with scann tool some what. There was no carbon bloching the valve as it was taken a part and cleaned. Would PC temp sensor have any thing to do with not going up to high idle when cold and staying around 650 when warmed up?
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Sunday, February 28th, 2010 AT 8:28 AM
Tiny
CARADIODOC
  • EXPERT
Regardless of engine or air temperaure, you should get a nice idle flare-up to around 1500 rpm at engine startup. If you do, I believe it has learned minimum throttle, and obviously the computer has control. It should come back down to normal within a few seconds.

Having a scanner makes life easier. Look at the various temperature sensors to see if their values seem reasonable. I've also been reading quite often about poor grounds around the engine computer, but I've never run into this myself. My '88 Grand Caravan developed a problem one day where it stalled at every stop sign unless I held the gas pedal down a little. I lived with it for two years. At one point I tried to solve it but couldn't come up with a solution. After two years, one day it started working properly again. That was about 8 years ago. It's still my daily driver and idles fine. I find it hard to believe I had a bad ground and it suddenly got better and hasn't acted up since. I live in Wisconsin, the road salt capital of the world. I'm lucky to have any metal left to call a ground.

Caradiodoc
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Sunday, February 28th, 2010 AT 1:26 PM

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