major idle issues

[mindstrap]

Ok here's the deal 1994 Pontiac Grand Prix GTP 3.4 DOHC Auto trans. about 130K miles on it now.
Here is the issue: When cold, it starts right up idles fine. as soon as its warm the idle just goes up and down from like 400rpm to 1400 and eventually stalls when it drops to low. Been driving it like this for a good 7-8 months--double pedal--to keep it from stalling. When driving it runs fine, gets up to highway speeds with no issues. However when parked, if I get the idle up it starts to skip around 4000rpm.
So far we've replace the idle air control module, plugs, wires, injection cleaner with no results but maybe a bit smoother running. Killed the battery to clear the computer.
Mind you that no check engine lights are on. plugged into a computer a while back it said the O2 sensor might be bad.
Has anyone experienced this issue?
Here are some past suggestions
-Overdue timing belt change
-mass air flow sensor
-leaking intake gaskets--haven't tested for that yet
Any help would be great!
Thanks
email me at mindstrap@gmail.com
Mike

[Superdave]

my 3.1 did that untill after i left the battery disconnected for about 10 minutes then did an idle relearn...

sounds like the IAC is out of sync with the computer for some reason.

[HayesPerformance]

When it does that UNPLUG the TPS sensor and let me know WHAT happens!


IF it levels out or stays at the same RPM then you have found your problem. IF NOT there are other things I can get you to check.


Regards,
Dave

[Juglenaut]

when it does that Try the same thing only unplug the map as well, what does it do?

Start troubleshoot with a cold engine

Also find the vac line supplying the fuel regulator, unplug it, start the car up, unplug the IAC if stalls leave it unplugged, try and restart if doesn't plug the vac line in try again if it still doesn't start you may have a clogged port.

start this portion with a warm engine.
Fuel regulator vac line unplugged:
If unplugging the IAC does not make the car stall, then unplug the IAC if the Idel changes but does not stall that is good, unplug the map does that make it stall...If not turn it off..unplug the battery for 20 min...Leave everything unplugged. Turn the key on listen for fuel pump, have a friend crank the engine while you observe the exaust, what is the color of the exaust?? turn the key off and unplug the battery for 20 min and plug everything back up, have a friend crank it while you observe the exhaust, what is the color??