1999 chevy silverado LS Z71 1/2 ton 4x4 5.3 eng. I have a backfire and Miss when hard throttle or pulling a grade on a highway. Check Engine Light On Too! Changed plugs and useing the E3 plugs, it ran great for 4 months and this problem has arrived... Thanks for the help! Clay

 

the e3 plugs are crap...go back to ac delco. they'll last longer. what other codes popped up?

 

Cleared codes but they were P0300 Random cyl. misfire and P0332 Knock sensor 2 circuit low input bank 2...... I bought AC Delco plugs today n will install soon.. After clearing codes it does run better but still misses n backfires when getting on it or pullin a grade on hyway. Thanks for the help...

 

the knock sensor is fun to change...its under the intake manifold. very common problem with silverado's 99 and up

 

Installed AC Delco plugs, reset codes and runs great, E3 Plugs are junk! still getting knock sensor code tho.. Thanks All Clay

 

mine did a similiar thing when i installed bosch oxygen sensors. problem disappeared when I replaced them with AC Delco brand oxygen sensors.

glad you got it figured out.