Greetings everyone.

Alright, here we go, have a 95 Blazer whiich has had all the gaskets replaced (including head). Has new plugs, wires, cap and rotor. After putting the engine back in, it ran great for a couple of months and now has developed a misfire/backfire from you know where. No CEL. Attempted to scan it and scanner could not communicate with computer (yes it was a scanner compatible with the 95). Vehicle idles alright, it's when you accelerate that it starts popping thru the intake and has no pickup. The other thing I have noticed is that the back firing gets worse as the engine warms up.

Whats been tested with no difference:
Pulled O2 sensor pre cat
Spride injector assembly
Lower intake manifold
Coil & Ignition module
EGR
MAP
TPS
2 cam shaft sensors
crank shaft sensor
Engine computer

The fuel pump is making a heck of a whining noise, however, when I checked fuel pressure. It was fine.

Any suggestions would be greatly appreciated. Does anyone think a faulty fuel pump would cause a back fire situation????

Thanks in advance for any input given.

 

Did you check firing order and that the plug on the rear of the distributor is plugged in?

 

Been checked twice, three, four times.... this problem appeared one evening while driving.

Changed the IAC. Still having the same problem. Going to change the fuel pump this afternoon.