a while back i started the truck and it just started poping, loud back firing sounds coming from exhaust pipe. found out cylinder 2's injector was bad. today i replaced it. still does the same thing. i know it was the injector from cylinder 2 cause when i unpluged that injector the backfiring went away. got a brand new injector and it does the same thing, any suggestions?

 

Damage to the cylinder? Maybe you replaced it with another bad injector. It happens sometime. Have you tried undoing number two again? Or at least run some injector cleaner or system cleaner?

 

Bad exhaust valve?
If you unplug the injector there is no fuel to cause the backfire...
Do a compression or leak down test!

 

good suggestions i will keep you posted

 

did the compression test it was good compression, used a multimeter and back-probed all electrical connections and they came back great. for some reason the signal just stays " on " too long. pcm was also tested, its good. is it possible i have a bad oxygen sensor? they have never been replaced, and the truck has 71500 origional miles. A few months ago when this all happend i tried Seafoam, but that did not help.

 

anyone?