I have an'86 coupe, basically stock with 81k miles on it.. It has been idling high (1300-1500 rpms) for a little while now and I had gotten some suggestions from forum members (thanks guys) what to look for (vacuum leak....). Well I found the vacuum leak and replaced the tubing. Started up the car and it didn't help, still iding high. i recently cleaned the throttle body and plenum, added a new TPS this week, and the IAC motor is less than 6 months old.

I went through the archives and found that this doesn't seem to be a rare problem, but I just could not come up with a concesus on what to do to fix it....

Well i followed the procedure on how to set the idle speed and TPS to the tee. The car ran fine without the IAC connected and the horrible sucking sound disappeared...Then I reconnected the IAC and the idle went right back up again and the sucking sound came back...
So I went through the precedure again and the same thing happened...as soon as I reconnect the IAC it backs out to wide open...But if I jumper the ADLD the motor does move into the completely closed position, so the motor is working........does anyone know why the ECM would keep that open fully. I have not gotten any codes either.

BTW, I have driven the car to work the last two days with the IAC in the extended position and removed the connector from the valve so it can't change positions, and the car runs fine....no sucking sound and it idles a tiny bit rougher than with the IAC, but other than that it runs fine.

Thanks for any suggestions,

I have learned more about my car (out of necesity rather than pleasure) in the last month than I ever thought I would, thanks to this forum (thanks to all who help out us novices)

Tom :smash:

 

At this point you realy need a scan tool to find find out what the ECM is seeing.

Possibly the coolant temp sw in the front of the block is reporting very cold temps so the ECM wants a high idle.

Jumper A&B, start the engine, watch the SES flash rate till it drops to around 1HZ (about 1-2 minutes); then rev to about 2,000rpm and hold for a second. If the SES on/off periods are about equal with a 1Hz rate that coolant sensor is ok because the ECM is in closed loop mode.

 

Thanks 65Z01 I'll try that and see what happens..........

Is there a possibility of the O2 sensor going bad?

 

when you installed the IAC did you make sure that the pintel was 1 1/8" extended from the base of the threads on the motor?

 

yes, i measured it each time I reinstalled it

 

Tom,

I see that you are located in Kenosha. Do you ever go to Union Grove (Greatlakes Dragaway)? We will be heading there on September 7th or 8th. Both days are "open runs". :cheers:

 

Hole Shot

I haven't been out there in a long while. A friend of mine and I have been thinking of going out soon, but his work schedule is difficult to work around and my car hasn't been running the greatest lately.

Thanks for the invite..............I'll have to check with the BOSS and see what the plans are for that weekend.

Tom :cool: