cleaned IAC..........still rough idle

89blkvet · 05-05-04, 03:20 PM

Well I have been fighting an idle problem for 6-9 months now. Removed IAC, it was very very dirty(gunked up), cleaned that and the port, re-installed, set the TPS to .55 and the thing has not improved at all...........HELP

86er · 05-05-04, 11:18 PM

What kind of idle issues are you having, too low, too high, surge, etc.....

89blkvet · 05-06-04, 08:37 AM

Well when it is cold, morning, it idles GREAT, after it warms up, it is very low and often hunts. It will often drop to 400 and just sounds VERY rough

86er · 05-06-04, 09:49 PM

89blkvet....

When the car is cold it idles higher until the engine warms up. A good place to start is by adjusting your IAC idle to 550 rpm, GM recommended 450 orginally and updated spec to 550. If you need help in doing this procedure, let me know.

SSTibet · 05-07-04, 07:21 AM

Quote:

Originally Posted by 89blkvet

Well I have been fighting an idle problem for 6-9 months now. Removed IAC, it was very very dirty(gunked up), cleaned that and the port, re-installed, set the TPS to .55 and the thing has not improved at all...........HELP

I had a similar, but somewhat lesser of a problem, with my Vette; idle became rougher and also low speed cruising became jerky. I could feel the hood trembling at these instances. I took the car to my mechanic yesterday and he cleaned both the EGR & IAC valves. Both were dirty and IAC's seat (where it is located in the cylinder block) had chips. He made no settings what so ever (TPS or other). He cleaned them all and the car is now riding so so smooth. I was used to have also a CES message, which went away... So, get all "idle related valves" well cleaned and if that does not work maybe you change them; they are relatively inexpensive.

Hope this helps

89blkvet · 05-07-04, 11:35 AM

I guess i should dtart by adjusting the IAC to 550......but I don't know how. I have removed the IAC and totally cleaned it and the port, they both were very dirty, the EGR valve and switch are new as well. Still rough

86er · 05-07-04, 09:01 PM

89blkvet....

It's super easy to adjust IAC.

1. Jumper ALDL pins A & B (two upper right) and turn the ignition on (not engine) for 30sec to extend the IAC pintel fully.

2. With ignition still On, disconnect the IAC wiring harness and start the engine. The engine may idle low and want to stall just give it gas to keep it running.

3. Then, using the set screw in the left side of the TB, adjust base idle to 550 RPM.

4. Shut the engine Off and reconnect the IAC harness.

5. Restart the engine and verify correct normal idle.

6. Drive car at 45 mph for computer to learn new adjustments