I need some help to diagnose what is wrong with my IROC. The problem is that when I am at WOT at anytime after about 4000RPM the car will backfire, immediate loss of power and the SES light will flash (not retain a code). For a little background on the car it's an 88 IROC with a 355, Trickflow heads, Ported Super Ram, LT4 Hot Cam, 1.6 Roller Tip rockers, and a 52mm throttle body. I have tried checking the timing (it's at 6 degrees), the EGR, the distributor is brand new, as well as the wires and plugs. I just am having a hard time finding the problem because it doesn't happen all the time. Also I have replaced the TPS and the IAC sensors on the throttle body and made sure to check the voltage of the TPS to be sure that it is sending the correct readings for idle and WOT. Any suggestions would be greatly appreciated!

 

ttt

 

Put a fuel gauge on it. I believe a drop off in fuel pressure could cause what you're seeing.

 

I have a fuel pressure gauge in the car, that I honestly have to revisit and see if it happens to indicate that the fuel rail is losing fuel pressure at WOT. I have replaced the fuel pump twice now, both times with a Walbro 255lph unit. I unfortunately don't have a scan tool that I can place on the car that will help indicate any trouble areas. Any suggestions to help me isolate what may be causing this lean condition? Also I have an Air Fuel Ratio gauge in the car that usually remains at Stotich (sp) rather than Rich or Lean - but again I know it's not highly accurate but I was hoping it would show me if I was running either completely rich or lean.