Runaway idle!

[danoduke]

My '99 996 idled perfectly prior to disconnecting the battery two months ago. When I recently reconnected the battery, started the engine, the idle speed hovers between 2500 and 3000 rpm! The gas pedal is free of obstructions, there's no binding of the throttle cable. So I followed my Porsche manual which indicated the DME needs to go through a learning and adaption routine after disconnecting the battery. Switched the ignition on for 1 minute without starting the engine, then off for 10 seconds. I did this three times to no avail. Any other suggestions?

[Loren]

:welcome:

The DME should relearn on it own usually takes just a few minutes - and I have not seen one idle that high after just a battery disconnect.

Perhaps the throttle butterfly is binding. Take off the air cleaner and the air box (rubber) tube.

Check the movement of the throttle buttery.

If it is a C2 then also check the idle control valve to see if it is stuck open.

Tell us what you find.

[danoduke]

Thanks Loren for the advice. I checked the throttle butterfly, it's not binding, the movement seems fine. Yes, it is a C2 but I'm not sure how to check the idle control valve to see if it is stuck open. I've attached a photo that might help in figuring this out. Notice the gap between the idle set screw and the throttle? I can force it down with a screwdriver, then she purrs like a kitten at 700 rpm, but as soon as I let go it jumps back to 3000 rpm! Very discouraging considering I spent the last 8 weekends replacing the clutch, main seal, and every hose, belt and filter on the car. All thoughts are much appreciated!

[Loren]

Have a look at these threads...

http://www.renntech.org/forums/index.php?showtopic=9299&view=findpost&p=45536

http://www.renntech.org/forums/index.php?showtopic=13120&view=findpost&p=64867

http://www.renntech.org/forums/index.php?/topic/21823-idle-air-control-valve-how-is-it-supposed-to-look/page__view__findpost__p__113375

http://www.renntech.org/forums/index.php?/topic/21574-rough-idlestalling-easily/page__view__findpost__p__112075

[danoduke]

Problem solved. As I was removing the throttle body I discovered the throttle cable had pulled out of it's slot behind the black plastic plug (not visible which is how I missed it). Once I repositioned it there's enough cable for the car to idle properly. Boy do I feel stupid! Thanks again for your assistance!