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1993 240 wagon 190k+
My latest adventures began trying to diagnose a ghost battery light in the cluster. My idle had been ok, but liked to creep down to 500 from about 700 (reading the tach). And it would occasionally hunt in between, and go higher as well. So, in my brilliant wisdom, I decided to fix the idle before addressing the battery light. Here's what I did:
- replaced PCV box and stub hose to trap. Cleaned trap, and upper hoses.
- removed, cleaned and reinstalled the MAF, snorkel tube (no visible cracks), IAC and hoses, throttle body (new gasket).
- verified IAC operation using ECU test 3.
I had to remove the TPS switch (another story), but have it reinstalled, adjusted per Bentley and verified operation per ECU test function 2. I also adjusted the throttle idle screw per Bentley as well.
Now I have the following symptoms:
- When fired up, the idle hunts between 1200-1700 indicated. If I crimp the IAC hose (no air flow), the idle comes way down to about 500 (or lower) and almost wants to die.
- If I give it some throttle, the oscillating will cease, and the idle sets in at about 1100 indicated. It never gets any lower, even after driving around.
- The hunting will randomly start during a drive, but only when coming to a stop. It never happens when the car is under power, even when RPMs are below 1700.
I suspect I may have a faulty IAC. I verified the IAC opens with 12v applied and moves freely. When it's closed, there is a slight opening. I did not play with the adjustment screw. I used TB cleaner on it, followed by some silicone spray. Could I have damaged it's ability to correctly respond to the ECU inputs thus causing the oscillating?
Any other tests to run? Thoughts and suggests appreciated. I really don't want to spend $100+ to find out it's something else.
Thanks.
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