Expert: Robert Summers - 11/28/2008

Question
2004 chev truck 1500 4x4 with 5.3 .it start out with code p0300 miss fire found #1 had a burt exhaust valve . took heads off hand repaired. put back together now it has code p0300 and  #1,3,5,7, has miss fire and plugs are all black .#2,4,6,8, are all ok.check for vacuum leaks found no leaks.check compression again all cyl has 150 lb.check all groud ok .check inj and pulse it ok.

Answer
Hi larry...did you check to see if those plugs were firing...check the plugs, coils and power /ground on each coilpack for the bad cyls...also check for short gap on those plugs...check for bad ground on ign module, check connections for corrosion...hope this helps