How exactly do you test the temp-sensor circut? Can I just hook up the multimeter (in voltage-mode) to the two connectors at the temp-sensor? I guess the ignition must be on, but do the engine have to run? I am a bit afraid to do some damage to the ECU...

I guess my car has the somewhat "older" system for controlling the idle (Probably due to less restrict pollution laws in Europe compared to US). At least you can adjust both the idle speed and mixture (CO) by turning some screws at the airfilter housing. The auxiliary air device controls the idle speed while the ECU controls the micture, am I right? Is there any way to test the air device? My problem could of course be a faulty auxiliary air device, and not be mixture-related.

Any info appreciated