I have an 88 GTA with the L98 TPI 350, 700 R 4, ported plenum and a superchip...well sometimes when I open it up and let the engine scream I let it go up to about 2nd gear and at about 4700 rpm i let off the gas and it turns off...why does this happen...AARON

 

Have you set the "minimum idle"?

 

Actually I don't really know to much about TPI motors, this is about the 6th day I have had the car....if you can please let me know how I can do that..THANKS....AARON

 

The IAC (idle air control) is what normally controls idle speed by bypassing air past the throttle plates.

If the IAC closes all the way, the idle speed is then controlled by an adjustable stop that keeps the throttle from closing completely. It's just like the idle speed adj for a carburated eng.

Different fuel inj systems use different methods for closing the IAC to set the min idle.
I'm in the process of building my first TPI eng, so I don't know exactly how it's done on a TPI.

On my CrossFire system, shorting the ALDL connections closes the IAC(s).

I'm sure a search will turn up some info for ya.