idle

[kyellan]

I have a 1990 Grand Prix LE with a 3.1 motor with 200k miles and is having trouble keeping idle. I have to keep it above 600 RPM to keep it started. A reader is not working on it because the CE is not on. So in responce i have started working on what it could be. Have replaced the O2 sensor, TBS, ICS, a tune up, and cleand out the TB. I have also looked for Vaccuum leaks and bare wires but are unable to find any. If you have any suggustions please I am stuck on what it may be.

[tblake]

Have you checked for proper fuel pressure yet?

[richtazz]

What are you referring to when you mentioned you replaced the ICS? Check for a leak to the MAP sensor vacuum hose that runs from the TB, under the UIM to the MAP sensor. If you have some vacuum hose laying around, you can temporarily replace it ouside without having to remove the UIM to inspect it. The MAP vacuum usually tees of the same vacuum line as the fuel pressure regulator.

[kyellan]

yes i have check the fuel pressure and the vacuum lines already but they seem to be fine.

[tblake]

how about the IAC (idle air control) motor, located in the throttle body.