idle revisited

[Louie Golden <louie@xxxx>]

Hey group,

I've done some more fiddling around with my car's idle... trying to figure out what the deal is. Initially I thought the cable was somehow not gettingenough tension to return the throttle arm to the microswitch, but it lookslike that is no longer the issue. The throttle can return the arm to closethe microswitch, but the microswitch doesn't make the car idle down every time like it should. I've lubricated the ever living mess out of every visable part of the throttle linkage from front to back on the car for reference. When the car is cold, it idles perfectly (well, as perfectly as a PRV CAN idle...), but as the car warms up, something suddenly happens and the car's idle jumps to 1500 and stays. I've watched it in the driveway as this happens, so since the throttle arm isn't moving, this tells me it's somethingin the automatic idle system. Several months ago I could blip the throttle, and the car would *sometimes* idle down to where it should, but this is no longer the case. The idle is getting progressively higher. After being driven, it now wants to idle at about 2000 rpms.

Over the last few days I've played around with some things. First I just unplugged the idle speed motor to see what happens. The idle will drop about 200 rpms sometimes, but will jump up other times when I try this, but when I plug it back in the car idles down to 800 rpms. So for an experiment, I tried switching out the idle speed motor with one from my old DeLorean. Thischanged nothing with the idle situation. So let me see if I understand howthe idle system works- the idle speed motor is electronically controlled by the idle speed ECU. The idle speed motor controls the throttle plates by vacuum. For reference, I also put on a new CPR over the weekend, and I alsoknow the O2 sensor is bad because the car hunts when it is very very cold.So I've deduced that my idle speed ECU is the problem after all of this. Am I correct? Is there any further ways to test it? I really don't want to chunk down that kind of money if I don't have to, but the idle situation is getting so annoying that I don't want to drive it any more. I would be grateful for any additional viewpoints or suggestions. Thanks!

Louie Golden
VIN 5252
NC plates "88 MPH"  

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