Erratic Idle

[pontiacfanatic]

Hello

I'm writing about two Grand Ams. One is a newer 2000 model, the other a 93 model (3300).

The 2000 model starts fine and runs without issue. Once it has been running for a while, the idle seems to drop to about 700 rpm and seems to be on the verge of stalling (but does not). Again, this occurs only after it has been running for a while and while idling (eg. a stoplight).

The second vehicle, the 1993, has a somewhat erratic idle (but does not have a tachometer) and also seems like it would like to stall when idled waiting at red lights.

Air filters are fine, new fuel filter on the '93 (the 2000 I don't know when it was changed), battery seems to be good (14.x volts continous).

I've searched the forums before asking but so far not found any similar scenarios....

Any help would be appreciated.
M.

[rixGAphx]

What engine/tranny on the '00?
Frankly, 700 sounds exactly right, and the PM maintians this precisely by modulating the Idle Air Control (IAC) module.

The SES/CEL isn't 'on', or you would have said so; therefore, no codes.

In any case of erratic idle, the first thing to suspect is a vac leak.
Check the vac hoses.
See my recent (10 mins ago) post in 'No Heat' thread about how to check for a vac leak.

-Rick

[dogred]

My wife's 2000 Grand Am SE car had some weird engine issues last fall. It would idle around 1600 and was a bear to drive. I changed out the TPS with no change.

I then took the Idle Air Control off and cleaned it out with a toothbrush and carb cleaner. (Make sure you let it dry completely before re-installing...else you get some really interesting SES codes!) After I got the codes to settle down, it started and idled at 600 rpm and verified with a scanner. The insides of the valve was extremely gunked up with a crusty/oily coating. You'll need a torx bit to take it off, I forget what size. It can't hurt to clean it out.

There is a vacuum hose near the IAC. My hose was crumbling after I did the IAC and was causing it to nearly die (rps dipped to 450-500 then pop back up).

[pontiacfanatic]

Thank you both. I read the reply from the other post made about erratic idle (mentioned by the first poster). I will try the advice given and see what happens. :)

[dogred]

let us know how it works out!

[artist723]

Hello I have the same problem with my 93 grand am 3300 I have checked for any vac leaks and have already changed the IAC module and found that the mass airflow sensor is what is causing this problem and is very easy to replace