yurizx6r

Hey guys, to make a long story short I am concerned that my base idle is too low and my IAC is doing more work than it should. I just installed a brand new 70mm throttle body (re-calibrated the TPS). With a new throttle body should I have to reset the base idle and play with the set screw or should I leave it alone?

If I leave the IAC plugged in the car runs fine and idles at 750, but it's not a perfectly stable 750 and the car smells a little gassy. Also, when I cold start it the rpms go to 2,000 and just drop down to 700 like it's going to stall (it does not) then back up to 1200 till it warms up. When I did a base idle test, I had to push the gas pedal in just to the car would stay running or else it stalled constantly. It was also strange that when I unplugged the IAC it whistled LOUD, and got louder the more I pushed the gas pedal down. I plugged the IAC back in and the whistle went away.... thoughts?

88 orangepeel notch

Maybe I'm not understanding correctly, but what set screws are you referring to?

I'd do a base idle reset with the new throttle body, only takes a couple minutes. Then see what happens. Drive the car awhile so ECM relearns any changes.

The cold start you described seems a little off. My car will idle at 1500 for the first minute or so depending on temps, but then drop and settle at 750/800 with a very slight surge between those rpms. I'm calling that good enough.

Let us know how it goes.

yurizx6r

I was referring to the idle set screw on the new throttle body.

When I do a cold start it will jump to 2,000 (or whatever) and then drop suddenly down to 700 (like it's going to stall, but it has not), then will go to 1,200 till it warms up, and slowly goes down to 750 when it's warm. It's almost like the IAC needs that split second to boot up and catch it before it stalls.

I'm just wondering if it's normal to have to do a base idle reset and touch that idle set screw on a brand new throttle body? I think so, but my buddy said "DON'T TOUCH THAT DAMN SCREW!!! They have it in that place for a reason and your going to F it up if you touch it."

Granted, it is running pretty decent, but it just does not seem right to have to rely on the IAC so much. Shouldn't you have a base idle around 700, so the IAC does not have to work so hard?

dawson1112

Part of the process of doing a base idle reset is setting that idle screw where you like your idle to be. 750-850 is fine.

If your car is idling at 750 and not surging or hunting then just leave it be, its hot hurting anything. They almost always smell a little rich when they are cold, its part of the way the engine maintains idle , kinda like the choke on a carb.

yurizx6r

Yeah it's at 750, but not that stable. It goes up and down slowly +- 25 or 50 rpms.

yurizx6r

So I said screw it........literally last night lol, and I gave the throttle set screw a few turns. I does not make sense to me that the IAC should have to work that hard and the car cannot run without it. I set the base idle to 750, turned it on. It ran lean for about 30 seconds (16.5-17) and the idle was at 900, and it whistled, so I backed it off a little bit. The whistle pretty much stopped and I let it idle for a few minutes. It idled at 800 pretty stable and at 14.5-15, so I'm thinking that's a win. I will do one more base idle test on it and I have to drive it to be sure, but either way I know I will find that happy medium. I think since the idle is more stable now at 800 I made the right call.

88 orangepeel notch

Good to hear, nothing wrong with adjusting the idle screw a hair, that's what its there for.

yurizx6r

Yeah for sure, but the only thing that I am a little confused about is why was it idling so lean until I made the counter adjustment? 16.5-17.0 is too lean for idle, and the RPMs were at 900, so why so lean? Granted, I get the computer needs to relearn everything, but wow that's scary.

88 orangepeel notch

16.5 - 17.0 AFR at idle is just fine, it's a little lean, but there's no load on the motor so it'll idle all day long and be completely happy there.

yurizx6r

Oh ok that's good to know. Thank you for all your help guys! I just installed the air/fuel meter in it a few months ago just after I installed the Trick Flow intake, so I'm still learning it.