IAC # question

[BuickMike231]

Hey guys, hope one of you may have some insight on this. I've been reading most of the other 'how do my scanmaster numbers look' threads for a while and can't recall seeing anything like this. All of my numbers look good on the scanmaster once the car's warmed up, but my IAC # is at 00 and never moves until I start driving. I did notice today it starts around 20-25 and continually drops too 0 as the car warms up. Also, my car idles fairly smooth, but one time when I start it it may be around 850-925 rpm, and the next time I start it it may be like 950-1000 rpm in park. Is this related to the IAC numbers being 0? If so, do I just need to do the IAC reset thing or is the 00 telling me it's shot? Any help would be greatly appreciated, thanks!!

 

[BuickMike231]

After driving the car a bit today I noticed that the 00 IAC reading only happens in park, with the car warm. Once I put it into drive with my foot on the break, the IAC numbers go right to 25-30 and the idle settles out to a really smooth 800-850 rpm. But once it goes back into park, the IAC drops right to 00 and the idle goes up a bit. Any thoughts on what this could be? Should I be worried about it at all? I mean the scanmaster numbers are close to perfect when in drive....just in park they're out. Pretty weird.

 

[BoostedEvIL]

I've been having the exact same problem for about a week. I'm also debating doing an IAC reset. Yesterday the IAC showed 175 for a minute or so after start up. Yours ever get that high?

 

[BuickMike231]

Mine has never shown that high ever. When it's in park it's at 00, and when it's in gear with the brake applied it's like perfect at 20-30. The car seems to idle fine though, just a tad high.

 

[Twistin6]

I have the same issue. Mine is at 175 at cold start. And after driving and warmed up in drive they are about 60-70. In park after warm counts down as it sets and idles to 00. With no change in idle rpm or sound just the values drop to nothing. My rpm in park is between 950-1000. I replaced my IAc but still the same issue. I have a high idle blm issue I can't track down which may be causing my high values. Does your blm numbers look to be in spec?

 

[Blazer406]

You guys need to all do the reset procedure... and verify there are no vacuum leaks.

Let me explain it this way.... IAC numbers are like a little ECU controlled throttle blade..... a way for the ECU to control the idle..... higher numbers.... means the ECU is opening the throttle blade.... lower numbers means it is closing the throttle blade... so.... if your numbers are at 00.... the ECU has closed the little throttle blade all the way... in an attempt to lower the idle.... since it cant reduce airflow anymore..... the idle at that point is uncontrollably (by the ECU) high..... so you need to adjust the big thrttle blade screw.... by closing the throttle a little.... and letting the IAC values come up....ideally... 20-30 are acceptable numbers idling in park... warmed up....

The theory is.... you adjust it until the ECU can adjust in either direction if it wants to... to maintain the programmed idle.....

Clear as mud?

Also.... once you adjust throttle blade to get IAC values back in line.... the TPS will likely need readjusting.... so do it as well...

 

[BoostedEvIL]

Thanks Blazer. I did the reset with temporary good results. Car got down to around 500 rpms. When I plugged the IAC up rpms came up to normal. Only had to adjust tps a touch because idle screw was already completely out. Car ran good for a few then went back to crap.

 

[Twistin6]

I have done the IAC reset procedure about five times now and the numbers won't stabalize. I notice a big difference with my readings in regards to engine temp. They tend to stabalize and hover around 50 when temp gets to say 175 or more. I can manualy cut the fan on and they will start to drop. At 160-167 they eventualy count down and bottom out and the idle or smoothness of idle doesn't change. If you weren't looking at the SM you wouldn't know anything is going on. As for vacuum leaks all lines are fresh and zip tied. And plenum is sealed. I fidled with it a bit more last night. Idle is at 825-875. I put a new 02 sensor on and within 1 min it threw a code 13 again (by the way this is the 5th one now). I reset it by disconecting the orange wire. Took it for a drive to let it learn and code 13 flashes again. Kept driving it for about 25 miles idle blm is at 131 and holding steady. I let it idle after driving for about 15 min. just to verify. As soon as I tickle the throttle they shoot up to 144-155 until I open it up a bit more and of coarse corrects to 128. After the re-learning it didn't throw the 13 code anymore or flash the check engine light again.

On a side note with the Gen II how long does it take to see an adjustment made to the low load fueling once you change a specific rpm range? Is it immediate or does it need to learn it? I changed it back and forth with no affect on blm above idle. At steady light throttle cruise 60mph blm is 145-155 but perfect at idle.

Didn't mean to steal this thread I just think we have some of the same issues.

 

[BuickMike231]

I finally did the IAC reset and have to say it worked very well. The car now idles very smoothly at around 825-850 rpm. The car's never idled this nice since I've owned it, it's a very nice thing to see.....thanks for the help!!