Hello all,

I'm new to the site and in desperate need of your expertise.

My 244 has always ran quite well despite its 490,000km and age, but it has always had a slightly high idle at ~900rpm. I just recently removed the TB and IAC, cleaned them thoroughly and checked their operation. The resistance of the pins on the IAC was ~22Ω for center to outside (both sides) and ~44Ω between the 2 outside pins. Applying 12V to center and grounding either outside pin caused some good movement. Also, measuring pins 10 & 23 at the ECU connector gave the same readings.

The TB moves well and I adjusted the stop screw and TPS as per the 700/900 faq. Testing at the ECU gives continuity for pin 3 at idle and the same for pin 12 at WOT.

Once everything was back together, connections checked, and car started, I grounded the blue/white wire behind the battery and attempted to set my idle speed. Well, the black thumb screw on the TB is in as far as it will go and my idle is 1500 at best, usually closer to 2000. There was a definite jump in idle speed when the ground was removed which leads me to think that the IAC is functioning. Also, squeezing the IAC hose shut (before the TB) brings the idle down to ~1000. Testing at ECU pins 10 & 23 (pin to ground) while running gives voltages of ~8.2V and ~10V respectively.

I am suspicious of both the O2 sensor and the coolant temperature sensor after performing some of the Haynes manual checks. Would these be likely culprits? I also do not have a timing light, but could likely get one if this might be a possiblilty for the high idle.

Any help is much appreciated, and sorry for the huge post; I figured being descriptive is likely more helpful than the alternative!