I have a problem with my ls motor. It has a idle issue. When cold it idles from 2-3k, eventually dropping to 1-1.8k. When I block the fitv hole in the throttle body it stops most of the time. However when I press the brake pedal the engine revs up to 4k and stays there until I release then it returns to idle. Any feedback. I'm guessing the fitv needs to be clean/replace but why does the brake effect the idle? I've search but nothing specifying idle issue with the brake.

 

how do the brakes feel?

 

At first I thought it was a leaky brake booster, however this swap is in a new shell and the problem persist. No cel

 

since you block the fitv, when it's at operating temp, and the idle drops, it indicates the fitv is sticking open. sorry. didnt see the fitv detail there. try another and see how that floats