"Resetting the IAC" is an old wives tale. Urban legend, or BS, whatever you want to call it. There's no such thing.

When replacing the IAC, push or screw the pintle into the IAC far enough that it doesn't bottom in the housing when you install it. Because this will damage it if it bottoms while being installed.

When the ECM powers-up, it sends the IAC more than enough counts to fully seat it, then opens it a programmed amount of counts to allow starting. After engine is running, ECM adjusts as needed for desired idle speed. That's all there is to it. There is no "learning" by the ECM for IAC control. Anyone who thinks there is, doesn't know how the IAC control works, or has never monitored IAC on a scan tool during start-up.



|UPDATED|11/3/2012 12:51:31 PM (AZT)|/UPDATED|

Okay, so should I be checking that at closed throttle the voltage at the throttle position sensor is @ .5 and if not decrease the screw until it’s near to that?  Does the ECM take the lowest voltage it’s reading now and assume it’s at idle, or because the voltage is higher it think I’m giving slight throttle when I’m actually at idle? 

So I wasn't able to figure out which of the 3 wires I needed to check as any combination I tried didn't give me any voltage reading.  My meter may be faulty too.  Anyway I went ahead and backed out the throttle adjustment screw all the way out, and then back in until touching and a 'tad' more.  Seems to be working great, and the idle is where I believe it should be.

first off you never adjust the throttlebody screw for idle problems,the tps has screws on slots to adjust the voltage,not the throttle plate.by doing this you will not have full throttle when you floor the acelerator,also this can cause a stumble.mid america sells a cable to just that for $14.99 with instructions on how to adjust the tps,all you need is a digatal meter.the part# 601-092.you now will have to put the throttle plate back to where it was  make further adjustments.tlavac

I was having the stumbling, and I knew that I didn't have full throttle options before as the screw was pushing the throttle plate more open.  I've since backed out the throttle plate completely and noticed the idle is where it is supposed to be, and I'm not having a stumble from a stop.  So I didn't adjust the throttle screw for my idle issue as I know that the ECM controls that, but having the plates partially open caused me to have a higher idle.  Definitely frustrating trying to figure out what previous owners have done or tried to do incorrectly.

that's the most painful thing is what previous owners have done. best to get things back to the proper position and go from there. the adjustment for the screw is from the factory manual. great to hear it is running better.

i'm glad its running better.get some factory manuals and it will help you adj the plate to factory clearance and then the tps will need to adj accordingly.get that harness and manuals and you will be all set.tlavac

Okay not to shoot a dead horse - but I went to the hardware store yesterday.  I wasn't in there for a horrible long time, and it was a hot day yesterday.  Finished my shopping, I got in the car and she started up a little hard, the idle was really weird - then she died.  So restarted her and she wouldn't idle.  After she would die she wouldn't start right back up but had to crank her for a bit.  I got her home with some fancy stickshift feetwork, she didn't idle at all on the way home so I had to keep restarting her.  At home I turned her off and went inside to tell the wife we need to take her in to the shop, and not a few minutes later went back out and restarted her and now the idle is running fine.  Had to make couple of more runs to hardware store later on - needed to get my home a/c working.  Corvette didn't repeat any of the idle issue and is now running fine.  Drove her into work today and no problems.  Nothing worse then phantom issues - anyone have any ideas what this is about?

Might be time to check fuel pressure, both when cold(first start), and after it gets hot. The fuel pump could be dragging when it heats up after runing a while, and not provide enough pressure or volume. If your pressure drops when hot, it's prolly time for a new pump. Could also be time for  a new fuel filter. 
An ignition module can also give these same symptoms.

Adam you hit it on the head.  So this week Tuesday got into the car for work and she started up, but no idle.  Started to drive down the street hoping it'd 'snap' outta it but still alas no idle.  Drove home to grab the wife's car and decided going to already be late for work, so we drove over to the shop (and of course now it idles fine.)  So days later (with no call back from the shop) I just got off the phone with the service writer and they have found that the fuel pump has indeed gone south.  She isn't keeping up pressure and showing low pressure on one bank.  I had to double question him as at first glance a fuel pump and lack of idle don't make any sense.  So what I was hoping was just a clean and check out the idle air control turned into an $750 job.  Blah .  Super glad we have this site though as I didn't realize my problem happened so recently (June) that she did this before.  So not that I have much choice but we're going to get a new fuel pump and filter put in.  They said I should have it back by next week... there goes my weekend of fun.