Car: 95 SC400. 150K miles, original ECU. TPS (IAC was incorrect in my orig post) replaced about a year ago with OEM. The adjustment per spec was impossible but I set it as best as I could.

This is my son's car and he drives with AC in AUTO and when I drive, I turn it off.

Issue: Idle goes crazy switching AC from on to off:

Cold start rpm is good and there is no hiccup and once the temp is near normal the idle starts creeping down.

The IACV eventually figures out the right adjustment but after few stalls (once) and almost stall (twice or thrice). CEL gets lit up but goes away when I reach 2200 rpm. In a day or two the idle is just fine (650-750) as if there is no issue.

Any insight into how the AC load adjusts the idle would be appreciated.

Salim

I assume you mean the TPS was replaced, not the IACV?

Has the ECU been serviced yet? When I was having my knock sensor issues that turned out to be the ECU, the A/C caused some bad stumbling when it kicked on and off at idle, and often triggered the knock sensor / limp mode.

You are psychic t2d2 .. it was indeed the TPS.

Salim

Educated guess. Getting the TPS adjusted to spec is impossible, in my experience, but the IAC has no adjustment that I know of.

Here, disconnect the battery. Remove the air inlet from the throttlebody. Push the throttle plate closed. Have someone else reconnect the battery while still pushing the throttle plate closed. Then have the other person put the key in the ignition and turn to the on position ( don't start) while you still held the throttle plate closed. Once the key is in the on position, reconnect the air inlet to the throttlebody (as soon as the key was turned on you can quit pushing the plate closed). Then start the car with everything turned off, radio, ac, lights. Let run for about 5 minutes at idle. Don't touch the accelerator. Shut the car off, you can restart and drive as normal.

If the throttlebody needs to be cleaned do it before the above relearn procedure

All I can say is WOW!. If it was not for you to share, where would I have found this information. I was looking for kick relay with adjustment with carbs. Thank you, thank you.

Will give it a try as soon as I can solicit help.

Salim

Did the procedure today. Started up fine at fast idle, and after warming up the idle came down with CEL.

Went for a short drive, and when ever RPM goes above 12k the CEL goes off and as I let the gas off and rpm falls below 1k, CEL comes on. Runs fine and idles fine. Have not turned the AC on.

The Code is 31 with OD off flashing.

Since the CEL goes away on a bit of throttle .. i think it is a slow leak on the intake side ... I hope I have not ripped the rubber connector between the the filter and the engine (that would make me mad at myself)


Salim