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Idle speed unstable

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My 1999 996 idle speed oscillates under some conditions. Also idles at either 800 or 1300 when the A/C is on.

Dealer diagnosed and said the throttle valve switch was bad. They want $200 labor (2 hours) to install a new one (this is after another $200 to diagnose it). It looks like it is just 2 screws and an electrical connector to install it. May need to also take the idle speed adjuster unit off to get at it (another two screws but with a gasket). Does anyone know if there is anything more to it than just removing and replacing like I describe? Anything to mechanically adjust or electrically reset? Do I need to use a new gasket when re-installing the idle speed adjuster unit?

The 2 hours concerns me some if it is really a 15 minute job but a bigger deal is that I have a 4 hour drive round trip to the dealer to get the job done -- so it takes a half day.

Any information on what it takes to do the job is appreciated. I do a fair amount of my own work and will do it myself if there are no tricks to it.



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C2 or C4? (C2 is non-egas and C4 is egas)

If your car is a C2 clean and/or replace the idle control valve. No adjustments needed. While you are there clean all the carbon from the throttle butterfly.

Thanks much for the advice, Loren. Yes, I have the C2. I sprayed some cleaner into the idle speed control while still mounted on the throttle body and it seemed to help some - can't tell for sure - still intermittently has the idle speed oscillation one time in my test drive. I will try to pull it off this weekend and clean more carefully.


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