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some ideas Posted by JimBlake [Email] ![]() ![]() ![]() In Reply to: Re: Thanks-Additional Info and Question:, JohnE 92s, Thu, 27 Jun 2002 07:34:36 Members do not see ads below this line. - Help Keep This Site Online - Signup |
I've struggled with surging idle on our '89 16v n/a & here's some thoughts.
Loose/corroded grounds on the engine near AIC might be able to hurt the quality of the tachometer signal which the AIC system uses as feedback. This tachometer signal goes to the ECU, so cleaning & re-seating the big wiring connector at the ECU might help. OTOH, that's inside the cabin so its probably pretty clean.
You've said it sounds like a lawnmower. If there's an exhaust leak near the O2 sensor, it might throw the measurement off. The sensor actually measures DIFFERENCE in O2 inside vs. outside the pipe.
I think the only way for a bad catalyst to cause this is if it is partially plugged. It's not impossible, but if its plugged enough to disturb the idle, it would be absolutely horrible at highway speed. If its not plugged, but the catalyst is shot, a smog test would fail but your ECU & engine wouldn't care.
A sticking rotor is not the only way for an AIC to fail. I had one that looked so good, & turned so smoothly, I refused to believe it was bad. When I used the ECU component tests to cycle it open/closed it worked fine. (Maybe I was too cheap to just replace it.) When I finally bought a new one the idle was beautiful.
Throttle basic adjustment? You say your AIC makes a hissing sound. I don't remember mine doing that, but I'll try to remember to listen. Maybe if your throttle is just a bit too open, then the AIC needs to be nearly full-closed, instead of being comfortably in the middle of its control range.
posted by 131.184.14...
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