High IAC count

[duber3]

What could cause high IAC count 56counts (high idle) when I put the car from drive to neutral or park
the IAC stay at the same count as it was in drive(the TPS is always at .44), shut the car off, wait 10 second, restart it and it's perfect, IAC 16, TPS .44
The chip is TT, brand new AcDelco IAC, the computer saw the Park/Neutral switch
I've try another TT chip, same result, changed all vacuum, new O2

thanks!

 

[granatl]

The whole purpose of the IAC is to allow air into the intake to control idle speed. So, if you adjust the throttle blade to be a little more opened, there would be less IAC counts.

 

[duber3]

I know that, the problem is that the IAC and TPS are perfectly adjusted, like I said when the car i fully warmed up, the IAC count is at 12-16
the problem of the high IAC count occur when I drove the car for a couple of minutes, like 15-30minutes and stop the car in drive, the idle is at 825rpm, iac count 56, that's normal in drive
when I put the car in neutral or park, le IAC count will stay at 56 and of course the idle is high, like 1100-1200rpm, I shut off the car, wait, 10-15 second, restart it and the idle is normal at 825rpm
and the IAC is at 12-16counts

 

[duber3]

Nobody have a clue why the IAC stuck at the same count when passing from drive to neutral or park??

 

[granatl]

It's strange how the ECM commands the counts, yet they don't change. If you watch the flags for the transmission, do you see them change when you go from drive to park?

 

[Eric Stage I]

Try resetting the IAC so that its in the 30-40 range when hot/park, instead of 12-16. (You'll have to re-adjust the TPS also.)
Drive it around a bit and see how that affects the situation.
Eric

 

[duber3]

Ok thanks Eric, I will try this, but it will be only in April
Still winter here

 

[Big Mitch98]

Just my two cents but I was having the same issue... Took out IAC carefully cleaned it out with brake cleaner re installed and haven't had the problem since. Lots of black crud came out....work great for about 6 months now

 

[duber3]

I did it, but I will retry to clean it again
thanks!