IAC replacement

Vinalero · 12-22-2008, 05:28 AM

Well as I had some problems with my idle that made me think my IAC was bad, I changed it. Now my Rpm doesnt fluctuate like it did before between 1250 rpm and 1500, but it is at a constant 1450 when the car is hot.

Is there a special procedure when replacing the IAC that you have to do?

With my mech, we checked for vacuum leak and could not find something that would look like it, sprayed brake cleaner on the intake flange, nothing happened. All hose connected, no holes.

My guess is that the car somewhat "learned" the past position of the previous IAC and now makes the car run at the same pace. I'm going to try something I saw on the net yesterday where they said you have to disconnect the TPS sensor while the car is running so it only runs on the IAC and recalibrate to its default position. I'm going to try also disconnecting the battery.

Any advice?

Nate's Alero · 12-22-2008, 06:12 AM

do what you said first, also watch this video, i know its a saturn, but its the same thing,

http://www.youtube.com/watch?v=ebWxk...eature=related
only it idles correctly in neutral and goes up while rolling in gear

[ion] C2 · 12-22-2008, 08:13 AM

agh wish you had HPTuners... you can see the target idle RPM, the IAC position, TPS, etc...

Gr1m · 12-22-2008, 08:17 AM

IAT sensor

meadus101 · 12-22-2008, 09:05 AM

When you disconnect the battery for 10 minutes, doesn't that revert the ECU back to a stock configuration and throw away the tuned data?

I was under the impression that it would revert it back to a learning mode, allowing the car to re-learn what it needs to adjust to under normal circumstances. If it's set to the old sensor, then this would solve your issue.

[ion] C2 · 12-22-2008, 09:07 AM

Quote:

Originally Posted by Gr1m

IAT sensor

and you could see what the IAT sensor was reading with HPTuners

if the IAT fails it'll think the IAT is -40F. i don't think that affects the idle rpm tables though, i don't have my laptop on me.

Vinalero · 12-22-2008, 03:22 PM

I doubt the IAT regulate the Idle. I just clearly have more air that goes through the engine when my foot is off the gas than normal.

Meadus, I was thinking the same, lets just hope it works.

Ion, just ship me your HPtuner

[ion] C2 · 12-22-2008, 03:27 PM

do a boost leak test, hook up a pressurized air source to the throttle body and listen for leaks

Vinalero · 12-22-2008, 03:30 PM

Good advice Ion, I should try that. My mech also told me something about a smoke machine they use to see where there are leaks, but he doesnt have it at home

[ion] C2 · 12-22-2008, 03:38 PM

ya you can usually just hear and feel the leak(s) but the UV reactive smoke is even better, it glows

i'm on my way to have another boost leak test done. we used it at speed industry to find my brake booster leak and "fixed" that but my problem came back a while later after driving, sucked, must've leaked again or something. we'll find out tonight.

Vinalero · 12-22-2008, 06:17 PM

Ok well update, I went out, took the foot of snow off the car and also around it. Started the car, brought it to operating temperature, idling around 1300 Rpm and oscillating from 1300 to 1400 slowly.

Then with the engine running, I unplugged the TPS and the idle came down to 1000 and variating slightly. So I guess I have my answer, its either the TPS that is bad, or (and I hope its not) when I installed my Supercharge, I tried to make the TPS wires longer by digging deeper in the harness to make some room for the TPS wires to reach the TPS at his new location (Those who installed the SC kit will know what I'm talking about). When cutting the tape around the harness, I accidently cut the TPS wires, both of them. SO I had to effing dig deeper in the harness, splice the cut wires, connect them back with those of the connector. But I didnt solder them in, just twisted them back together, I put some new electrical tape tightly on top of them and called it a day. I just hope no corrosion got in there.

Beholder88 · 12-22-2008, 07:35 PM

I bet you any money it has something to do with those wires not being spliced, or sealed properly. I've had a similar issue with exterior lighting. Also, when you install a new IAC, you're supposed to find somewhere you can drive at 40mph for a couple of miles straight without stopping. When you stay at that speed, your computer will "relearn" the new IAC setting and it should run alright after that. I was having that exact same problem on a 3.1 in a Grand Am, did the 40mph thing for two miles, and she was as good as new.