ok this is a werid problem when im sitting at a stop light if i put the car in gear the idle gos up and down up and down if i take it outta gear it idles but idles high. whats wrong?

 

http://www.teamfc3s.org/info/articles/idle.html This makes for a interesting read.....but does not answer your question. I'd bet money that the described problem is only while the engine is cold. Has a lot to do with the ECU getting a signal from the neutral switch telling it that the car is not in neutral anymore.

I'm guessing that if the idle on the car was set at 750(initial set coupler installed) and the variable resistor set right, that this up/down at idle would go away. Just a guess. I'm pretty sure its mixture related resulting in the bac varying the rpms up and down. Just a guess and not to be taken for more than a guess.

 

no actually the car does it when its warm not cold. and does it at random doesnt do it all the time.