IAC torment

[Mephisto]

I'm getting a code 35 and idling at 2k rpms.

If I disconnect the battery and the harness on the IAC, then reconnect the battery a few minutes later and start the truck... shouldn't the idle change even slightly if the IAC is the problem?

I've searched and read a bunch of threads about IAC, TPS, vacuum leaks, and high idle... But no one is having this problem... exactly...

So I start the truck, idle is around 2k. IAC position 38. Code35 comes on... IAC position starts dropping, and so do the RPMs... then I get to normal idle (don't mind the rough idle timing is still off) and IAC is at 0.

I have done the innertube on the upper IC trick with only a tiny amount of hiss coming from the TB (which I read is common with our TBs). I've pulled the upper IC and sprayed an entire can of starting fluid around the upper, and lower intake and the TB, with no spike in RPMs, and I pulled the whole vacuum hose kit I got from sportmachines off and went through that to make sure there were no cracks or tears.

it's gotta be one of 2 things... either there's a leak somewhere that I'm just not finding and the IAC is adjusting all the way down to 0 to compensate, or the IAC is crap.

I'm gonna go waste more money on another IAC, just to rule that out. But after this, it's either going off a cliff or to a shop... the towel has been thrown.

and to top it off, I just locked the keys in it.:rant: Just the cherry on top for how this entire week has gone.

PS if anyone has any hi-def maybe even multi-angle video footage of a typhoon completely engulfed in flames, please PM me. This would be my porn at this point.

 

[dgoodhue]

Re: IAC torment

It sound like someone adjust the throttle stop on throttle body to me. The IAC passages couple also be clogged up preventing the IAC from fully closing as well.

 

[Quickstop [UK]]

Re: IAC torment

X2

 

[Mephisto]

Re: IAC torment

Nope... I've backed that screw all the way out when the idle was up at 2k but it still didn't bring it back down to 850.

Also pulled that bottom plate off the TB a couple weeks ago and it's all clean.

Went to Napa, 2 gmc dealers, chevy dealer, and vatozone and no one had an IAC valve in stock. So I'll have to wait for Napa to get one on monday. GMC dealer quoted me $176.20 :rotf:

Also, I just want to note that the idle doesn't always go back down... I've started the truck up, and it's idled at 2k for over 5+ minutes with no change at all.

I beginning to wonder if maybe it's an electrical problem between IAC and the ecm.

After I fixed the rocker arm on the #1 cyl, I drove the truck around 15-20min at a time for a few days with no problems. I go to buy gas, fill it up, start it up, and idle is at 2k. Next day, start it up and it idles fine. Drive it around, turn it on and off a few times... no problems. Come home another day start it up, idle at 2k and doesn't come back down after waiting 10 min. Shut it off, curse it, and go inside. Next day, start it up, idles at 2k, few minutes later it comes back down and idles like normal, and I go drive it around a bit. Next day idles fine when I start it up, go drive it 15min, park it, get back in to leave... idle at 2k again.

The intermittence is what's driving me crazy. I keep thinking it's fixed and then the truck just laughs at me.

 

[liquidswords88]

Re: IAC torment

A iac from a throttle body 305-350 will work. The one I am using right now came off of a 1989 full size Chevy truck. Easy to find, easier to remove.

 

[TYTILIDIE]

Re: IAC torment

If the IAC is at 0 and you are idling 2k RPM, the ECM is trying to cut air supply to lower that RPM. So in short, if the IAC is at 0, then it is closed all the way which should mean you have a leak somewhere. If the pintle has been played with it could be that it is in the wrong position. You can reset the IAC to ensure that the position is correct. Have you tried charging the intake of the turbo to see if you are leaking anywhere?

On a side note, I have reset an IAC a few times and have seen the pintle strip the inner gear.

 

[Mephisto]

Re: IAC torment

This is datamaster this morning... idling fine and IAC normal, but still getting IAC error. So this would lead me to believe there isn't a leak. I drove it around after this, and later the rpms kicked up again... I pulled over, put it in park, the CEL came on, the rpms went back down to normal, and I drove it home. Hooked up DM and it's the same as the pic below. Normal idle and IAC position.

I'm gonna swap out the IAC this week and see what happens... but this is getting pretty aggravating. I don;t think a leak can leak and then not leak, and then leak and not leak. If it still happens after the new IAC, then it's got to be some sort of electrical problem with the ECM and the IAC harness err something.

 

[Static]

Re: IAC torment

Possible lower gasket leaking into crankcase? Like after it warms up it comes unsealed making it intermittent?