Hi.

When I attempt to calibrate my IAC, I set the ecu into diagnostic mode to move the IAC. Key off. Unplug IAC and remove diagnostic jumper. Start engine. I've read that most people set their idle to 450 rpm. For some reason I cannot set mine below about 1200, and the throttle plates are completely closed. Is this normal? When I plug everything back in, the engine seems to be idling at normal speed, but will sometimes be off 200 + - rpm from the target rpm. Do I have a vac leak somewhere? Engine seems to run superb otherwise, besides a lean idle.

-HD

 

https://www.thirdgen.org/newdesign/tech/tpimod2.shtml

Here is the article on how to set min-air.

It sounds like you are not unplugging the IAC before turning the key off.

This is the way I do it.

Bring engine to normal temp, turn off.
Jump A&B in ALDL.
Key on for 30 seconds.
Key still on, disconnect IAC connector then remove jumper from ALDL.
Start engine and set to spec.
Turn off engine and reconnect IAC connector.

 

You're supposed to disconnect the IAC while the key is still on? Oooohhhhhhh! That makes sense though. I performed the correct procedure last night, then reset the TPS. I'd have to say that the truck idles MUCH better now.

Boy do I feel dumb. Just got my aldl cable made up last night. Going to make some runs today and do some logging.

Thanks so much.

-HD

 

Hey Eric,

Glad to see you still here.

You helped me get my TPI conversion going last April.

I had the "stuck in fuel trim cell 4 or 10) whichever it was and you clued me right in. That old TPI is screaming in my old "Rust Truck".
Running great. (after only 31 chip burns)

Just wanted to say howdy.

Jim

 

Howdy - Glad it is idling better now. When the key is shut off the ECM sets the IAC to the desired park position which is in the PROM.

VetNutJim - happy to hear you got it running well.