How many steps should we be logging at idle on a '91 tbi 305? I've been logging and tuning the fuel for the last couple of months and i've got the car runnin like a champ now, i've been following "Free Tune" and I read about the 5-10 steps at idle, mine seems to be around 16 when I first start? Are there factory specs for IAC or does the ECM control it for the most part?

Thanks.

 

The ECM will open the IAC however many steps it takes for the engine to maintain the set idle speed. You can control how many IAC steps are required by adjusting the idle screw on the TBI unit. Turning the screw to the right will slightly open the throttle meaning the ECM doesnt have to open the IAC as much to maintain proper idle speed. Turning to the left will close the throttle causing the engine to want to stall and the ECM will open the IAC however many steps are needed to compensate.

 

That's great Darkshot, but are there a recommended number of steps to ensure proper IAC movement from idle through WOT?

 

i have a 7.4L TBI on a 350 CID. engine cold is 90 steps. engine fully heat sink is 0 steps. WOT which i ran last night shows 50 steps @ 90 MAP. idle commanded to 850 rpms and idles 900 with throttle stop screw fully retracted.

 

The 5-10 figure you posted originally is stock and is correct for a healthy TBI motor. It is what I shoot for.