Just like the subject says, I'm having a problem where the car will rev immediately up to about 1600 rpm on startup and slowly come down to regular idle. I hooked up the laptop and it seems that when I turn the car off every time the counts jump up to 130. So when I start it the next time it starts out open almost all the way and then slowly returns to about 40 or 50 counts at idle of 850. Throttle body, IAC, and tps voltage are all clean, set, and operational.

Why is it doing that? How do I fix it?

 

That's pretty much normal. The PCM is parking the IAC high for the next start.

 

so why does it come down so slow? when I start the car warm it should go straight to normal idle. Plus inbetween shifts I feel the rpm's lagging staying up too high and stuff.

 

Take off your throttle body and pull off your IAC. You might have a lot of carbon build up in those passages that are affecting your IAC operation. Might want to just go ahead and replace your IAC at the same time. They are not very expensive.

 

The passage is very clean. See guys I think I have the problem figured out, I just don't understand whats causing it. When I shut the car off, the IAC spikes to 130 counts or even slightly more! So when it starts up, it's starting w/ the IAC almost at full throw, so when the rpm's come down slowly it is actually the IAC regaining it's normal idle position of about 40 counts. The computer must think the car is naturally going to die so it's trying to compensate by opening the IAC all the way, however, all that is doing is allowing way too much air for the next startup. The problem only started occuring after I put on the supercharger and the OBDI computer (engine was stock at the time). What could it be???

 

Did the problem start on its own or did you change somthing? Learned idle speed sounds like it is not reset. Most cars have a drive cycle that has to be relearned. It is a specific bunch of b.s. that you have to follow. I`ll look it up tomorrow at work and repost the drive cycle for idle relearn and repost tomorrow... ok?

 

Okay thanks man. The problem did not exist when I last drove my car before it went under the the blower, injectors, OBDI computer, and anything associated w/ the blower on a STOCK engine. The throttle body is a stock bored to 52mm but the problem existed with a stock 48mm TB as well.

 

I looked at some old logs. My IAC goes up to 130 and even higher when I shut it off, too. Apparently that is what it is supposed to do.

 

Hmmm, then maybe mine falls off too slowly. I will check it out thanks shoebox. About how fast does yours fall off???

 

On a warm engine, they come down near normal in 6-10 seconds.