whaneyrhs

hello i have a 94 c4 with lt1, i recently changed optispark because it broke up in high rpm. while i was at it i changed the water pump. when i put it all back together it ran great for 20 mins, parked it and the next morning it started backfiring. i did not ground the wiring harness could that have burned something up? i changed the opti again and now it is only missing on #7 cylinder. it gets spark but no fuel, new injector on cylinder still a dry plug. i replaced maf sensor, map sensor, and fuel pressure regulator. now what?

whaneyrhs

Could it be the ecm?

arbee

Since you appear to be just throwing parts at it and hoping for the best, go ahead and replace it. If that doesn't work, try the power steering pump, starter or the A/C compressor. If all fails, as a last resort, you could get an FSM and follow the diagnostic charts.

Purple92

I'd suggest getting a "noid light" and hooking it up to the injector lead for the #7 injector. See if it flashes (meaning if the PCM is telling it to inject fuel) when the car is running.

If the noid light tells you that Cyl 7 injector is not getting a fire command - you need to figure out why. It's most likely a wiring issue - just do the diagnostics.

C409

..... I would start @ #7 and work my way in that direction , wiring-wise .....