I don't know if this is the correct section for me to ask this question but I am going to ask it.

I have a 1999 honda civic si EM1 and I just recently put a 65 MM throttle body on my car from bdl. Well here is the problem ever sense I put that on my car will idle differently every time I stop also I get a CEL every once in a while that states that the IAC system has a failure in it. I have cleaned that IACV and also adjusted the idle screw and the tps is set correctly, I even thried adjusting the TPS. Still when I start the car and it warms up it will iddle between 1000 rpms to 1500 to 1600 and changes everytime I stop. Then also some times it will start jumping between 1000 to 1500 rpms. I have no idea what is going on that would cause this so I thought that I would ask you guys to see what is going on. thanks.

 

Come on no one knows.

 

Well, my guess would be that you are getting changes in airflow, seeing as you havent changed your injectors, but have changed your throttle body.

There is a chance you have a very small vacuum leak at the throttle plate.

Take some carb cleaner or starter fluid and lightly spray around the TB to see if it changes the idle.

Be sure not to spray it INTO the TB opening as it will definately change the idle. Just lightly spray around the outside with the car running to detect changes.

This will help you better diagnose your problem.

 

I think the carb cleaner is the best way to diagnose the vacuum leak. Have u set TPS voltage correctly?
Also try and switch the IACV for another and see if that makes a difference.