austin8388

1996 LT4 with 46,000 miles. It's mostly stock. 5 and 7 cylinders are not firing. #5 is misfiring twice as much as #7 but both not working. I replaced opti-spark, all wires and plugs. Test lights show both 5 and 7 injectors are getting power. I swapped out good injectors in the bad cylinders but still have same issues. I guess a compression check is next. There is no smoke from the exhaust and no oil in coolant or coolant in oil. ANY IDEAS?????? Thanks in advance.

bad-zr1

Just a quick thought, make sure they are not swapped. 5 and 7 are the easiest to get mixed up as they are next to each other in the firing order.

all4c4lt4

96GS#007

austin8388

Ok. swapped 5 & 7. Same results. Checked compression on all odd cylinders and all readings are correct. I drove it for about 20 miles and got no improvement. Maybe it is an electrical issue in the harness.....? I think 5 and 7 injectors are are tied together but not for sure. I'm out of ideas. Anyone?

Quiktrp94

Valve spring or rocker? Can't imagine anything else.