2000SSNB

iTrader: (4)

Hello,

after finishing my LT install (with cats) etc, I noticed that once the throttle
is over 80% there is sporadic hesitation. After some checking with my scan tool software I noticed that cyl 4 develops a lot of misfires during
WOT (>80%). At idle or below that and partial throttle I get almost none.
The kooks headers use brand new stock seals. Plugs seem okay - coils
are original (stock) of our 2000SS.

Any suggestions? Maybe I should check compression on that cylinder?

Thanks,

Gert

speedo

iTrader: (15)

How is the plug...? Did you drop or somehow hit it during the header install... I had put in a new set once and had the same deal, turns out I dropped one and cracked the plug.....they don't like being banged around.

Maybe try swaping a plug from another cylinder... That is a place to start if you haven't already...

tomss99

could be the plug... could be a cracked valve spring but i highly doubt that since their stock springs.... maybe your wires not on all the way.... or like they said cracked or bad spark plug

jimmyblue

iTrader: (11)

I'd suspect one of maybe three things. One, excess plug
gap can make the arc fail at higher cylinder pressures.
If the misfire is pronounced at lower RPM as well, this
is a good possibility. Two, along similar lines if there is an
insulation fault in the plug wire or the coil, that's another
way for the spark energy to sneak out without paying.
Three, a crusty injector could run out of delivery early.
That one ought to be accompanied by some knock
retard, you'd think.

2000SSNB

iTrader: (4)

Thanks for the suggestions - by process of elimination - it was the spark
plug. 2 fine cracks on opposite sides in the ceramic insulator. Problem
is fixed and no more misfires in cylinder 4.

Gert

speedo

iTrader: (15)

Happy to hear you got it figured out. That little $hit is frustrating...