Check the throttle linkage. There is a switch that signals idle condition. I dont remember which way it works, but when on idle it is in one state (closed or open) and when the gas pedal is depressed it is in the opposite state. Maybe you just have to grease the linkage.

Saumil

__________________
Saumil S. Patel

Actually, I just remembered, there are two switches. One is on the throttle body and the other is near where the accelerator cable comes from. Check both.

__________________
Saumil S. Patel

Thank you - I will check both switches this weekend and post findings. I assume a faulty switch may give conflicting signal to the control unit, i.e., both throttle closed and open simultaneously.

Could also be the idle control valve sticking, you can disconnect the valve, unplug the air hoses and unbolt it, then spray it liberally with solvent. If you have a 9v battery, you can connect the poles to the leads on the valve to energize it and help expose more of the valve surface. Do this outside and be careful about sparks - don't want to set yourself on fire!!

Can also try cleaning out the mass air meter - if you remove the air filter housing and depress the meter plate, spray a bunch of air intake cleaner up towards the meter plate hinge. You'll need a spray can with a plastic extension to get up there. Have some paper towels to soak up the draining solvent from the bottom of the housing.

Anthony

that really sounds like an idle control valve issue...really does...

Hi everyone -

Well, it seems to be an idle position sensor issue as Saumil suggested. I cleaned idle control valve and even bought a new one. Having some experience with K Jetro, only suspect for fluctuating idle has been idle control valve (or as Porsche calls it, auxiliary air valve). I did not realize KE Jetro has idle position sensor switch as well as throttle position switch.

When I cleaned idle position sensor switch's connectors (to wiring harness), problem went away immediately. Switches are still original to this car so both switches probably should be replaced. But for now, it runs perfectly.

Thank you everyone for your input.

I do have one more questions though. When I replaced idle control valve, I was also trying to replace hoses. One has a connection for start-up valve and start up valve is secured by 2 hex bots. I managed to strip one of them (after soaking in PB Blaster for 2-day). Anyhow, do you have a recommendation for extractor/method? As there are electricals around, heat is not an option.

It seems thatI spoke too quickly. Car was idling just fine for a whole day but idle hunting came back next day. I am still suspecting 2 switches - throttle position sensor (variable) and idle position sensor (on/off). Does anyone know testing procedure for these switches? Also, I cannot find throttle position sensor by itself - do I need to purchase the entire throttle housing, if the throttle position sensor is faulty?

Thank you!