Hi Everyone,

I have been ripping my hair out on this vehicle and would GREATLY appreciate to get ANY help I can.

The Vehicle is:

1993 GMC P/U 1500 Auto

Engine:

Rebuilt 5.7L with Vortec heads, Edelbrock EPS Performer intake, Performer Cam, Flow-Tech OEM replacment headers, Flowmaster Exhaust, MSD PRO-BILLET "drop in" Distributor, NEW Stock TB installed, ALL SENSORS REPLACED NEW, MSD 8.5 wires and other then that its a stock 5.7L TBI

ECM (STOCK):
BIN: BHAS
PROM: 16194300
SCAN ID: 4325

- The engine compression is great and even
- Valve timing is set right
- Ignition timing is set to the 0* TDC
(With ESC tan/blk wire unpluged of course)
- Vacuum is excellent

PROBLEM

When the engine is cold and in a Open Loop, it runs very excellent and very strong.
AS SOON as it's warm and goes into a closed loop it Backfires Badly and even stalls when you floor it or step into it hard.

I've been trying to figure this out and I don't know whats wrong!

Thanks!

Regards,
David

 

The only way to tell is to put a scan tool on to see what's going on. Otherwise you're just throwing parts at it. If you are going to do that, start with the O2 sensor. Just because something was replaced, doesn't mean it's good.