What's up guy's I have a 1988 iroc camaro 5.7 tpi I recently installed hedman headers, the next day I felt as if it was mis firing, so I went ahead and changed spark plugs, cap rotor, o2 sensor. When I'm at a stop on drive with foot on brake it start to idle rough/vibrate, as soon as I put it on neutral it idles fine. I also checked for vacuum leaks. Bubba and I are stumped. I know I could always come here and get valuable pointers and advice. I appreciate any help and suggestions.
Thanks in advance.
Sal.

 

Confirm the firing order of the spark plug wires. You might have plug wire on the wrong plug.

Sometimes you won't be able to feel the rough idle out of gear.

 

I've checked firing order a few times I'm sure it's correct, but I'll check again in the morning.

 

Im open for any more suggestions

 

With the car STONE COLD, walk out to it with a squirt bottle with some water in it. Start it up. After running about 10 seconds or so, squirt a small amount of water on each header tube.

One (maybe more but probably not) will act MARKEDLY DIFFERENT. Check everything about that cylinder; spark plug, burnt plug wire boot, etc.