High Idle Problem.

[jaycafe]

I've got an odd problem with a high idle. I traced it to a pvc intake grommet/gasket (that must have gotten sucked into the motor), replaced it, and the idle dropped from 3000rpm (!) to about 1100rpm....still too high. When the motor is cold, the idle will be at 1100; when it warms up, i need to stop at a light...put it into neutral...and the idle will drop down to 600 and then stay there. I can't find any more vacuum leaks. Could it be a problem with the tranny acting up (it seams to be shifting a little late also).
Anybody have any ideas on what i should tackle next??
The car is a 1996 grand am gt with the 3.1 V6.

[rixGAphx]

Certainly could be the tranny, more particularly, the Vacuum Shift Modulator.
This (or a kick-down rod) was the method of controlling shifts on 40 years of previous non-electronic trannies.
All electronic trannies don't even have a vac modulator.
The 4T60E electronic tranny in the '96 GA has both electronic shift (solenoids for 1-2 and 2-3) AND this vac modulator.

Follow the vac hose from the intake manifold to the front top of the tranny.
Make sure the hose is tight.

Mebbe even replace the part, one of the few tranny parts that can be replaced from the exterior.
About $50 for a new one.

[arthurgoboom]

You're saying the idle is high (1100) when the engine is warm and the car is in gear, but then the idle drops down to 600 when you shift into neutral?

I would say 1100 idle is normal for cold startup, mine idles around 1000 for the first 30 seconds or so.

[rixGAphx]

No, the V6's should be down around 700-800, warm or cold.
They have more rotating mass, and a couple more horsepower at idle, which allows them to idle lower without stumbling from the AC clutch engaging suddenly or other such sudden load.

[sudden_impulse]

Both my GA and my brother's GA (both the 3400 V6) idle around 1050-1100 rpm on a cold start up (cold being less than 50* outside, engines fully cooled down, usually overnight). I was told an idle that high is normal, but once it warms up it should drop to about 600 rpm, so unless the idle is staying at 1100 when coasting, it sounds normal to me.

[jaycafe]

I haven't got around to checking the vacuum hoses going to the tranny yet. The idle starts at 1100rpm and stays like that well into the normal temp range. Its almost acting like an "old stuck choke on a carb". It will drop back down to 600 rpm when its no longer under load (neutral), and completly warm.
Fun stuff.:roll2:

[rixGAphx]

Idle is controlled by the Idle Air Control valve.
Yours might be sticking.
Do a 'search' here about cleaning it.

[Jasonldrummer]

I have somewhat of the same issue.
I have noticed that my RPM's are high at highway speeds. When I go around 65mph. the RPM's are a tad bit over 3000. What should the Tach say when going these speeds? And sometimes when I start the car the engine would "rev up" then go to a more normal level of RPM's.
I also thought that maybe the transmission isn't shifting into the last gear when driving. Any thoughts or possible solutions about this would be great!

[speedemon77]

i to am having a idle problem i had the iac valve cleaned and it lasted about a mounth i think it may need to be replaced. How do you change it ? where is it located, and how much should i expect to pay for one?

[speedemon77]

oh yeah i have a 2002 gagt 3.4 liter custom side exhaust , cold air intake , iridium plugs , and a performance chip on the way , next year comes the turbo kit.