Hello everyone once agin. I have posted, searched, and hit all around but still this high idle problem. The car is 87 IROC 5.7 TPI. The problem is it is not showing any codes and everything checks out, TPS voltage, idle setting, timing, no codes, no vac leaks, runs good, good power & torque, everything checks out. The only thing it does is act like its cold all the time, like when I start it in the mornings its perfect but, after it warms and I pull in to get gas and shut it off it still acts just the same as when I first start it in the mornings only insted of holding the idle at 1500rpm for a while till it warms it just starts at 1500rpm then idles right down to 700. Also when I pull to stop lights it stays at 1500rpm till I come to a complet stop then it idles right to 700 but, I have to come to a complet stop, if I keep rolling at any speed, 10mph or even 5mph, it will stay at 1500rpm. I have unpluged the cruis module and it didnt help any. I have had it hooked to data master and it seems to be showing the right engin temps to the ecm and everything. I can unplug the iac and the idel stays right down where ever I unplug it and I have changed and cleaned 3 diff iac sensors and they all act the same way. I dont know what to do but I know theres someone here that together I know we can fix this. Please help Im stuck and dont want to have to leave my IAC unplugged. Thanks and HELP lol......

 

Stock chip?

 

yea stock chip, I have headers, 6A MSD, 1.6 roller rockers, plenum ported some and runners, venom 21# fuel injectors, 40 over flat top pistons, IAC coolant bypass. But the problem started all of the suddun one day after I ported the plenum, runners. It was fine after the rebuild just one day I pulled them off and ported and put back together and this was the way it acted. its not a leak because I can unplug the IAC and the Idle stays where I unplug it at perfect.

 

Look closely for a leak between your MAF and the plenum.

To troubleshoot better, make sure your IAC is in the fully closed position and then unplug it. It's part of the setting minimum air rate routine.
You would then need to drive it a little with the IAC fully closed to see if the idle variance is still there. I would also plug off the vacuum lines for the HVAC, EGR, FPR, CCP ports, and brake booster for testing.

 

well I have been driving with the iac unpluged and fully closed as outlined in setting min air. And as long as its unpluged it stays where I set min air. It seems as if theres a delay in the ecm telling the IAC to close off and the speedo has to be at 0 as well.

 

If the ECM is causing the IAC to react that way, then it's likely due to some out-of-spec feedback from one of the sensors.

As far as vacuum leaks, this would only effect the MAF output since the ECM doesn't measure vacuum directly.
I think the best bet is to hook up a laptop and do some datalogging to watch the various sensor output.
For instance, if the TPS readings are out of spec, that can definitely affect the IAC action.
What you described as a symptom sounds a lot like the throttle follower routine function.
In custom apps, it often needs to be adjusted to improve drivabililty, but since you have a stock chip it leads me to believe that one of the sensors are out of spec. I know the TPS and VSS play a big part in that routine. There may be others, but I can't think right now.

Anyway, with datalogging you can closely follow the IAC count to see for sure what is going on there.

 

finnaly some good help lol. Yes I have datalogged and from what I can see the vss and tps show good. I could send ya the data file if you think you can tell something about it. And yea it seems as if something is misadjusted but stock chip so it has to be a bad sensor but I just cant find one that is showing bad. the tps seems good the ecm engin temp seems good the ait seems good vss reading correctly now the maf shows a reading in my program too but Im not shure what im looking at when I look at its reading its in grams per sec I think or I think I can change it to a percentage but like I said I can send you the file if you can look at it and tell anything. Either way im getting ready to put on my afr heads and comp cam and I would love to get it running right first. I have to get it running right this problem is killing me lol. ohh yea my data loggers is tcc datamaster . I also have several others I can log with if you are more familiar with them just let me know and I can log with one of your choice if it would help. I just used datamaster because it has alot more info such as the IAT and MAF readings.