Anytime I go full throttle, my IAC goes out. I put a brand new IAC on and drove it around and it was fine. As soon as I gave it full throttle the brand new one went out

Anyone have any ideas or seen anything like this before?

Scott

 

does it just look dead or is there is a scanner you can confirm this with? I dont get it Please explain more . . .

 

My car was running perfect until yesterday (motor has about 2500 miles on it) I gave the car full throttle for the first time with the new motor yesterday. I took the car to about 6600 through 4th gear and when I let out the car would not idle below 2500 rpm. I kill the car and restart and it still will not idle below 2500. I scanned the car with Datamaster and the IAC read 0 @ idle. That told me it was dead. I bought a new IAC and @ idle it read about 40 which means it is working properly. I gave the car full throttle and now the new IAC does the same thing, reads 0 @ idle but now it idles at about 2000 rpm and eventually comes down to about 1100. Which I have my car programmed to idle at 950.

I thought it may be a vaccum leak or a blown intake gasket but I could not find anything at all.

I NEED SOME IDEAS!!!!!

 

Well, just because the IAC says 0 and it's at 2500 after a WOT run doesn't mean the IAC is shot. It very well could be a tuning issue, with not enough idle steps added in, or it could be something that's causing it to read the 2500 as the idle and resetting itself there. If the IAC was truly going out, I don't believe that your car would idle because it would close everything off.

 

After that car did this, the only thing I did was put a new IAC in. I didn't reset the computer, reprogram, etc... Just changing the IAC fixed the issue perfectly. The idle steps were fine, it idled great, when I reved it up the idle came down exactly like it should and idled fine. But as soon as I gave it full throttle the IAC started acting up again.

 

sounds like you have a vacuum leak somewhere.. checked for sticky throttle blades? the IAC is supposed to control the amount of air entering the motor when the TB blades are closed and there are no vacuum leaks. If the IAC reads 0 that tells me that NO air is needed to keep the motor idling.. not that the sensor is dead. Since no additional air is needed from the IAC then it has to be getting in from somewhere else. If the IAC was not working at all.. the motor would not run without cracking the throttle blades.

 

I looked for vaccum leaks and could not find anything. When I replaced the IAC I scanned it and the IAC was at about 40 at idle. I drove it around and checked it again and it was at 41. So it was working fine. I then took the car out and gave it full throttle and that is when the IAC went to 0 at idle.

 

You are reading what count the pcm is commanding the IAC to be. It is commanding it to be 0. The problem is not the IAC, it is tuning or a leak somewhere. You can keep putting in IACs and it is going to do the same thing every time until you find and fix the real problem.

If you are not using a stock throttle body, there could be issues there.

 

I have a BBK 58mm tb on there now. I took the tb back off again and took the IAC out and cleaned the air passage for the IAC real good and looked over everything to make sure the tb blades were not sticking or anything and it looked fine. I put everything back together and scanned the car, the IAC count went to about 30 and then fell rapidly to 0 then the car idled down to about 1000. I turned the car off and back on and the IAC count went to 121 and then came down to about 36 where it stayed. I gave the car some gas and the IAC went up and came back down to 36. So the IAC was not stepping properly at first and now it is again

I think it has something to do with the BBK (like you suggested shoebox). I am going to put my stock tb back on next week and see how the car acts with it. If it works fine the I know for sure it is something with the tb. If not,

 

After your WOT blast maybe the throttle blades are not getting closed well. You might compare TPS readings to get an idea. You also may need to play with the throttle stop screw. Probably, the blades are staying open too much and driving the IAC counts down.