Sooty #7 - ZR-1 Net Registry Forums

XfireZ51 · 06-19-2017

Recently, I started experiencing a case of gray/blackish exhaust exiting the rear. Motor no breaking up. And at first I chalked it up to car sitting around during the winter. Blowing out some carbon. But it has continued. But only when I go WOT.
I pulled some plugs for a compression check and #7 was not in good shape. It was pretty black and sooty. I replaced the plugs and did about 700miles to MI this weekend. Car ran great, ~ 24-25mpg. Pulled new #7 plug and again sooty.
Checking plug wire and injectors w engine hot:

Injectors (primary/secondary) both check out at ~15ohms HoT.
Also checked plug wire resistance thru coil HOT, 14Kohms end to end. Same as other
cylinder pairs.
#7 also tested out at 220psi which put it a bit below the 228psi average for the 8 cylinders.
Compression was:
Lft Rgt
235 235
210 230
215 245
220 240

06-19-2017	#1
XfireZ51 Join Date: May 2007 Location: Chicagoland, IL Posts: 9,708	Sooty #7 Recently, I started experiencing a case of gray/blackish exhaust exiting the rear. Motor no breaking up. And at first I chalked it up to car sitting around during the winter. Blowing out some carbon. But it has continued. But only when I go WOT. I pulled some plugs for a compression check and #7 was not in good shape. It was pretty black and sooty. I replaced the plugs and did about 700miles to MI this weekend. Car ran great, ~ 24-25mpg. Pulled new #7 plug and again sooty. Checking plug wire and injectors w engine hot: Injectors (primary/secondary) both check out at ~15ohms HoT. Also checked plug wire resistance thru coil HOT, 14Kohms end to end. Same as other cylinder pairs. #7 also tested out at 220psi which put it a bit below the 228psi average for the 8 cylinders. Compression was: Lft Rgt 235 235 210 230 215 245 220 240 __________________ [SIGPIC][/SIGPIC]Former Membership Chairman Former ZR-1 Registry - BOD 1972 Corvette 4speed base Coupe SOLD long time ago 1984 Corvette Z-51/4+3 SOLD 1992 Corvette ZR-1 Aqua/Gray #474 SOLD 1992 Corvette ZR-1 Black Rose/Cognac #458 2014 Honda VFR Interceptor DX Last edited by XfireZ51; 06-19-2017 at 06:16 PM.