when my car idles for a while warming up it seems to start to run like crap.stumbles etc,what would cause that? 3.8 supercharged..126k..good plugs,wires MAF...

 

I'm no mechanic, nor have I played one on the but I was just having the same I and it turned out to be one of the injectors was bad. If you can unhook the electrical and use a multi meter to check resistance on the injectors. They should all be about the same ohm reading, if one or two is off that would be your problem. Good luck

 

I have a broken screw in the IAC..i ordered a new one,heard that can cause it too..

 

There's a few issues that could cause it. When a car is cold, it's dumping extra fuel into it to warm it up quicker, and wait for the sensors to get warm and in the ready state, before it switches over to making AFR adjustments based on the sensors.

If it's not your IAC screw messing you up, it could be a fueling issue or an oxygen sensor starting to go.

 

It does it when its warmed up also...i hve not put my scan tool on to see what it says when it happens..