Hey guys,

My car is a 1997 z28 with a 6-speed. I recently took my intake off and had it ported - as well as added a 58MM throttle body in place of my old 52MM one. Now everything is back together and idles and runs fine.
My only problem is that the car wants to stall when I push the clutch in and slow down. I always have to put it in nuetral and have one foot on the gas while braking in order to keep it from stalling. But other than that, it runs fine while idling, accelerating, and cruising.

Does anyone have any idea what this could be? Is there any adjustments that could be made on the new 58MM throttle body? Or does this sound like a vacuum leak? I was thinking it might be that the computer tune is not updated yet - but wouldn't it run bad all the time if that were the case?
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thanx in advance for the responces...

 

Take the TB off and make sure the blades are not making contact with the bores. You want to adjust the blade stop screw just enough to where you can barely start seeing sunlight through the blades.
Make sure your IAC motor is clean/plugged in.
Other than that if you disconnected the computer while doing these things it may need to relearn. After I installed a 58mm and LT headers on mine it would not idle correctly until after about a week of driving. It would also die or stumble for a few seconds before it'd return to a normal idle.

 

vacume leak maybe

 

I never disconnected the computer at any point - just all the sensors and vacuum hoses necessary to get the intake off.

For adjusting the blades, you don't want them to be fully closed??
I did not do any adjustment to the throttle body before installing it - I got took it out of the box and put it on....

 

I thought of that. But wouldn't the idle surge a lot and run rougher during ALL conditions if this were a vacuum leak?

 

iac.

 

So, how do I fix it?

 

Try putting the 52 back on and see if the problem goes away. If so, you may need to do the TPS slot mod.

 

I'm gonna agree that I bet its IAC related. There are several ways to over come this. Drill a new IAC bypass hole as most aftermarket TB's don't have this. You could open up the TB blades some more, or even add a IAC bypass hose that goes from the intake elbow to the intake manifold.

 

vacuum leak will cause a higher idle, but wont necessarily make you run like crap during any conditions
i suspect a fault with the idle air control system, you may need to do that bypass mod