dwillms

Hello,

Since I've had my car for the past 3 years or so, it has always idled high. When I first got it, around 1300 RPM, tried adjusting IAC, now 1000-1100 RPM.

So today I finally decided to try again. Followed correct procedure listed on the boards here. (BTW, my TPS is set perfectly, if that makes any difference). I can't get my car to start AT ALL when the IAC is disconnected. No matter how far in or out I turn the adjustment screw, it won't start.

Now, my car idles high at start, but when it is warm, it idles low enough that it almost stalls (500-600 RPM I believe). I know the ECM controls idle, but I still think there is some reason it is idling that high.

Is it my actual IAC valve that is causing me problems? I have cleaned my throttle body blades.

-Dustin

UPDATE: Tried to do the procedure again when the car was at normal operating temperature, still didn't work. Now, I reconnected my IAC, and my car now won't even start anymore. Issues...

Trickster

Are you following the procedures in the article that VADER has posted in the tech article section?

dwillms

Well, about 3 sentences in, anyways I jump the ALDL, wait 30 sec, disconnect IAC, take out paper clip, try to start car. As soon as I disconnect the "connector" from my IAC, and try to start the car, it won't start.

Also, I tried adjusting the IAC screw to see if that would make any difference in starting the car, but it didn't do anything, no matter what I did to it.

I waited about half an hour, now tried to start the car, it runs with IAC connected. Idles about 1000 in Park, about 800-900 in Drive.

-Dustin

Trickster

That screw that you were turning is the Idle Speed Adjustment screw. That is what you turn after you have the car running with some one in the drivers seat holding the brakes and the car in gear. By turning it, you are throwing the TPS setting way out the door and the ECM is trying to compensate for it. Turn the screw back to somewhere close to where it should be and re-adjust the TPS setting. Then try it again after reading the whole tech article.

thirdgen88

How long after start-up does it stay high like that? Does it go to something reasonable when you put it in gear?

dwillms

When the car is cold, idles 1100/1000. Warm, drops maybe to 900. Cold idle in drive is 800-900, warm it gets to 600 or so.

The only reason I was trying to turn the idle screw was because the car wouldn't even run when I disconnected the IAC, so I was trying to see if that would make a difference in even getting it started.

If the screw is in far enough, it holds the throttle plates open a little bit, which would then bump up the TPS a little. I'm just not understanding exactly what I should do, the article makes perfect sense to me, except for the fact I am stuck about at Step 2 of the procedure .

-Dustin

Trickster

I believe that in one of the steps there that it mentions giving it a little gas if it is hard to start.

gta ta

UPDATE: Tried to do the procedure again when the car was at normal operating temperature, still didn't work. Now, I reconnected my IAC, and my car now won't even start anymore. Issues... [/B][/QUOTE]

You have to give it some gas to start with the IAC motor all the way in. It will idle at like 400 so it will stall. It has to re-learn. You then go drive it. But if yours is like mine in 15 miles the high RPMs are back again.

I have been fighting a high idle in my 86 TA for years. Done everything. EGR, intake gasket, injectors, mat, computer and chip, tons of other things. vacuum is 22. I have come to the conclution it is an `86 T/A problem. Had GM machnnics look at it. Noone has an answer. I'LL pay anyone $100 if they can tell me why I have a high IDle. The computer is doing it but why.

dwillms

Have you got into DIY Prom burning at all, or just got a replacement ECM and chip? I'm starting to get into it a little, I'm switching from the $32 to the $6E ARAP file that was used in 1989 cars, so I'd like to see if that makes any difference in my idle.

-Dustin

gta ta

NO I haven't. Vader had told me that early '86 Proms were defective so I went to the dealer and gave them $90 for a new with the part number Vader suggusted. I figured if I burnt my own chip I would mess something up and lean the engine out and burn a piston. I know it is the computer causeing this issue.

If it makes a differance let me know.