Here is what is happening. When I start up the car at first it is fine except it will idle high, maybe 1.5-2.0k rpms. Once I start moving however, if I am holding the clutch in or cruising in neutral,whatever the speed, the rpms will "jump" between 1k and 1.6k rpms. It will rev itself up and then drop and rev itself back up again. very annoying. It seems to stop and idle fine once the car stops moving but even sometimes once I stop it will keep doing it. It has progressively gotten worse over the past week. I also noticed that sometimes if I turn my lights on, or turn my ac on it will idle smooth again, but still high. Does this sound like a vacuum leak because ive looked all over and can't find one. has anyone ever experienced anything like this?

 

car is stock with stock tune the last time anything was changed was the tranny fluid a couple months ago

EDIT: and there is no check engine light

 

Check your idle air control motor maybe?

 

two best bets are idle air control valve or throttle position sensor, both easy fixes in easy spots

 

wouldn't that cause the engine light to go on?

 

not always. If there is carbon in the passages it can restrict the flow as well.

 

anyone else have a similiar experience? With more seat time have I come to notice that it only happens when it is cold outside. If it is warm the symptoms are a lot milder, but are still somewhat there.

 

yes mine does it... i dont know what it is.. i have hp tuners.. not sure if ican tune it out or not

 

How is your clutch? Is it fully disengaging right away?

 

From my knowledge a sensor sets a code when it gets out of a certain range....depending where they set that point depends how far off it has to be to set a light...A sensor can still be bad but not set a light because its in range but at the wrong time...ex. if a tps goes from 1-5 volts, at idle it should be 1 volt and if its screwy inside and its putting out 5 volts then it wont set a cel but means its fucked up, get it?

About the problem what if you just disconnect the tps or iac and see if it still does it? I'm a noob with gm cars but there should be a default map for the tps it can run off of with it unplugged, if it still does it then its not that