Hey guys, my 86 Trans Am with an 87 TPI and 91 ECM running a stock 91 GTA 305 TPI bin file idles at 1100. I can't get it down without backing off the timing and then it backfires and bogs and stutters. I also get 4-8mpg.

I have my VSS wired from the tranny to the buffer and then to the Speedo, pretty much how it was wired from the factory when the car was carbed. Will this affect my idle by not having the VSS signal going through the computer?

Here are some other mods that I have done to the engine area,
Crane Cams PowerMax 2050, MSD 6A & Blaster 3 coil, 52mm ThrottleBody, stock 87 TPI heads, Dynomax headers, pacesetter 3" cat-back, SLP Dual Cold Air intake, and I guess that is about it.

My car is a 5 speed 305.
if you want to see a vid to hear the idle, here it is,
http://www.donpagevideo.com/video/ZepherWS6.mpg
In the beginning of the video, the car is cold so it is idling at 600, but when it warms up it stays at 1100.
Thanks

 

Yes, the VSS has to be working correctly for the ecm to figure things out. The IAC is also a throttle foller and speed dependent.