I recently knife edged the throttle body butterfly valve on my 68mm throttle body and ever since then my car seems to idle quite high (1200-1600rpm). I made sure not to reduce the diameter of the tb plate and there are no leaks in the hoses that attach to the tb+maf. The funny thing is this only seems to happen sometimes, then other times the car will idle normal and all will be right with the world, this leads me to think that its some kind of software issue, would this be something a tune would remedy?

btw other than this mod my car is a stock N/A.

 

it takes very little to cause a high idle. knife edging removes material.. period, opening up that gap a thousandth or 2 is all it takes.

i had a high idle when i first installed my 74, but it has come down since as the ecu has to relearn idle tps position and such

 

When I first described doing this I did not knife edge, rather radius the plate. I do not suggest anyone remove the plate as the screws can loosen and back out which is in the motor...............yikes.

The real gain was to remove the step on the inlet of the throttle body and knife edge that to allow less turbulence at the inlet. This is a precision part and spacing counts, rounding the plate is all that you want to do to reduce the square edges. Woody

 

being that this only happens some times i would look at the gasket there sounds like there is a leak somewhere,, mine did that when i had a manifold leak, ( first start high rpm put in gear ,,,it's good for a while stop at red light ,,high again ,,- vac leak jim