That dirty rotten son of a............

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..........K car. What is it with this car?

Now I've established that the throttle bodies are fine. They have a little side to side play but that did not effect the high idle.

Turned the set screws on the throttle body stops back a bit. That helped for thirty minutes.
Then the car fell back into its same pattern: tweak it, change something and you are rewarded with thirty minutes of driving with a normal idle speed, and after that all bets are off. Did not unhook the battery (that will also yeild 30 minutes of normal idle driving) this time.

Loosened the throttle cable about 1/16 of an inch. Again thirty minutes of normal idle driving.

It randomly drops back to normal idle, so randomly in fact that often times I think I had something to do with it i.e. gun the engine - idle goes back to normal, turn on the AC - idle goes back to normal. Unfortunately none of that is consistently reproducible.

Got frustrated and started pinching off every hose under the hood that could cause a vacuum leak. Nothing. Finally I grabbed the hose to to Idle speed air control valve and smushed it with my hand. That brought the idle speed down. Could not tell how fast because I was outside the car but by the sound of it it was slower than normal idle speed and almost stalled the motor. This was happily repeatable.

So now I have a new set of questions

1) Knowing that I just recently replaced the idle speed control assembly what are the odds that this is still the culprit?

2) If something in the car is sending the Idle Speed control unit the wrong information and making it run at a higher idle what could that be?

3) Given that everytime I "fix" the car I get 30 minutes of pain free driving could this problem be related to temperature? It seems that even if the engine is off for a short time and I tweak something I get in and it runs ok for about thirty minutes.

4) Could it be the computer? Does it take thirty minutes or so to input new data after a change has been made? If I do nothing but unhook the battery and hook it up again I also get thirty minutes of good driving.

5) It seems alot of folks are having problems with high idle speeds. What gives? What do those Dodge folks have to say?

Sorry about all the questions; as frustrating as this problem is I've always enjoyed working on my own cars and I'm learning alot about this car by tracking this problem. I really have a hard time letting anyone else work on any of my cars; I just enjoy the sense of accomplishment one gets when finally everything comes together and works right.
 

Joseph Houss

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This might be a silly question...

Did you replace the battery yet?

If not, this could account for the 30 minutes of running time, as the battery might be at a full charge, but as the run time continues, you might be going below necessary voltage to drive the idle sensor.

My '96 coupe was experiencing idle stall-out upon deceleration, new battery fixed the prob!
 
OP
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Thanks;

I was reading in the shop manual last night that the battery voltage was one of the inputs to the Idle air control.

And it is the original '97 battery (Shame on me).

Apparently a low voltage input leads to widened pulse widths at the injectors.

I will try and get that changed this week.
See if that helps.

THANKS!
 

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