V1PWRED

Well for some reason after 8 months of 0 problems, I finally have developed a slight misfire under boost. It only happens under hard boost, not in first or second so much when it goes through the powerband very fast, but in 3rd and 4th especially. I have oem style plug (ngk-tr55) at .042 gap when I checked. Tested all coils resistance, seemed fine. Tried a heat range colder plug which actually caused this misfire to be worse. Mayby try a smaller gap? like .038-.035. I am really thinking a tune...I've been using vortech's tune for these months, had it dynoed just for A/F and hp numbers. The tune isnt the best, but the A/F was safe and thats what i was concerned about. Just odd that now a problem would arise. Any input would be nice, thanks guys!!

99StangGTTN

the most common plug ran with superchargers is typically a NGK TR6. I would recommend a gap of no larger than .32" but on all stock ignition I would run closer to .28"

2000GT4.6

Change the plugs and gap em down. Sounds like spark blowout to me.

ottos

My stock 99 developed a misfire after the weather changed last fall. I hadnt driven it in weather below like 40 deg before and it just started all of a sudden. Checked all hardware, and nothing was wrong, and nothing should have been wrong since it ran great 3 months before. Out of options, I got an updated PCM calibration and finally its about 95% fixed. Its $80 though, so i've noticed its not the most popular fix for this problem around here.

But this is a really common problem on these engines.

V1PWRED

Yea the tr6 is the colder plug I had tried, only caused it to be worse (poor idle and a misfire in all gears even under normal conditions) I will go ahead and gap these way down to .32 and see how that does.

2000GT- you are probably right, I was digging through the forums here and I read a couple on spark blowout, will try the .32 gap as stated above and see what happens

thanks guys

99StangGTTN

the tr6 is not too cold of a plug for your application.

V1PWRED

When did I say it was? I simply said that my car ran worse on it and I would rather stick with a TR55.

jlw2387

Honestly, just take it to your local speed shop. If theyre good guys thell hook you up.