Ok so I was running against my friends 5.7GTO at work today for ***** and giggles. Everytime I got into 3rd (twice we ran) I would get a flashing check engine light and I would get a missfire on cylinder 4. I have BKR7Eix NGK Iridium plugs at .040 gap any ideas? Ive never ran my car that hard so I dunno?

 

try some different gaps.

0.37
0.35

0.40 is at the very limit of the widest gap our cars like.

 

uh ohh you might need new #4 piston... is your dipstick popping out yet

 

how is your car running? misfire on #4 usually means you cooked the #4 piston.

 

Oh na ok long story!!!! When I was doing the spark plugs I keep getting interupted by a damn dog that was loose in the neighbor hood. Anyway, I didnt gap plug number 4 it was at .065!!!! I was stupid, anyway, I cleared the code with a scan tool today and regapped them all. Anyway car = smooth and rocks. Just when I was in 3rd about 80ish it went nuts. At all .045 they seem to be ok. Im going .040 when I get a 2.9

 

Wow .65 is huge , can't believe it didn't present itself in everyday driving or at idle . When i was at .45 my car idled like **** .

 

No not at all not until 3rd gear near like 80 something then I could feel it miss. Very odd huh? Car is damn smooth now but I felt no miss at all and had no CEL lights before either