Idle, Pulsed Rev's?

99' GASE 3400

Today when I came home from a friend's I decided to turn off my AC/Fan Speed to 'off', while I was in my driveway in park. Next thing I know my rpms dropped straight to 500 almost killing the engine... then it rev'd back up past 1000 and pulsed back and forth untill it found a happy medium at around 600-650... I was messing around and soon found that I can do a short rev to around 1000rpms and it'll do the drop to 500-600 and just pulsate high - low - high untill it just levels out at 600-650...
Temp was 200-210F

Any Ideas?

i had the same problem, but no fan issues, so try turning them back before you do anything, anyhoo u'r idle air control valve is prolly bad, it's a little cylinder in front of the car connected to the throttle body, well it is on the 2.4, go to sutozone and ask them what it loks like , it costs 67.99 in texas.. lol in usa i should say.

You either have a dirty IAC motor (not bad; doesn't need to be replaced, just cleaned; very easy) or a bad throttle position sensor (TPS) or possibly even a bad MAF.

I would 1st try cleaning the IAC motor
then replacing the TPS
and then looking into cleaning or replacing the MAF as a last option

beyond those 3 options there's lots of things that could be causing misfiring/hesitation, but my guess is that it's either your IAC motor or your TPS.

If you need more info about any of those 3, let us know.

i tried to clean it, and even when i replaced it i wen't to autozone and the part they have listed for the grand am isn't even the right part, the one on my car has a rubber plugger on the end, and the one they gave me has a metal thinggy, sooo good luck with that problem it seems it's never going to go away. how would you clean it anyways? you can't get the metal casing off the motor.

You have a 2.4. We have 3.4's. Different story.

To clean the IAC for the 3400, you will need to 1st of all remove the intake up to the throttle body. Next, remove the 2 star bit screws holding it in (it goes into the side of the throttle body at the top of it). Pull out the motor. It is a base, with a spring-spindle end that actually goes into the TB, with a rubber plunger at the end. Remove the entire unit. Using throttle body cleaner, clean the spring / shaft of the spindle, and clean the rubber end the best. Avoid spraying TB cleaner directly into the IAC motor. Next, pull open your throttle plate and stuff paper towels underneath it. Using TB cleaner, clean / flush the hell out of the IAC motor cavity in the TB, as well as the TB and throttle plate itself. Just rinse the hell out of the entire TB and IAC cavity with throttle body cleaner, until all black residue / gunk is gone. When everything's nice and clean, put back together in reverse order.

you really dont need to remove the TB to clean the IAC. I'm sure, with the miles you have though, on the back side of the TB butterfly is carboned up, doesnt hurt to clean it.

Some IAC's have a rubber tip, but the metal will work. My boss just cleaned his the other day, was metal tiped, and clleaned the TB cavity w/cleaner. After drying it out replaced, the idle was so much smoother.

Thanks guys for all the input. Just remembered a few days ago I removed the stock box to have a look at my MAF screen w/ the metal and it was all black.. I assume carbon build up =\ I can only imagine the IAC is the same... theres alot of miles on my GA .. and I can only assume the previous owner didnt take to much care of it with tune ups and such.... I read the name and I think a big chunky burly white guy with glasses who has a cat that rides with him *shrug* Never know... Ill go take a look at the IAC tomorrow when theres daylight

seems like if you baby you car, the carbon builds quiker than when you run the shit out of it. Maybe i'm rong, but thats how mine works. Pos ga's.

And Gir, if you unpluged the MAF when you had look'd at it, and then after hookin it back up it rev'd up and down, this is normal while the maf recalibrates.