Multiple misfire
Thread Starter
Drifting
Joined: Mar 2006
Posts: 1,872
Likes: 7
From: Richmond VA
Multiple misfire
Car is stumbling badly at and above apx 4k rpm. I got a P0300 one time, and a heated bank 1 O2 sensor one time (at idle). We changed plugs and tightened the gap to .30 from the .35 I was running. Replaced all the gaskets on the intake. The misfires seem to be primarily limited to cylinders 6, 7 and 8. Once it misfires, it starts running super rich. There is a slight stumble at idle, barely noticeable. I currently have 100 octane in the tank (which I have run many times before).
Leak down found nothing.
Ideas?
'03 C5Z; P1 blower at 7#; stock fuel system with BAP
Leak down found nothing.
Ideas?
'03 C5Z; P1 blower at 7#; stock fuel system with BAP
Tech Contributor
Joined: Jan 2007
Posts: 19,450
Likes: 1,155
From: Dyer, IN
Car is stumbling badly at and above apx 4k rpm. I got a P0300 one time, and a heated bank 1 O2 sensor one time (at idle). We changed plugs and tightened the gap to .30 from the .35 I was running. Replaced all the gaskets on the intake. The misfires seem to be primarily limited to cylinders 6, 7 and 8. Once it misfires, it starts running super rich. There is a slight stumble at idle, barely noticeable. I currently have 100 octane in the tank (which I have run many times before).
Leak down found nothing.
Ideas?
'03 C5Z; P1 blower at 7#; stock fuel system with BAP
Leak down found nothing.
Ideas?
'03 C5Z; P1 blower at 7#; stock fuel system with BAP
Thread Starter
Drifting
Joined: Mar 2006
Posts: 1,872
Likes: 7
From: Richmond VA
I hadn't run it in a couple months. During that time, I pulled off all the engine bay covers/tanks/intake and had them painted. I shortened the BAP cable, but soldered it back to the original dial controller. Installed a DynoJet Wideband.
Our first thought was that I didnt get the intake seated properly. So, I replaced all the gaskets and re-installed.
Our first thought was that I didnt get the intake seated properly. So, I replaced all the gaskets and re-installed.
Instructor
Joined: Jul 2007
Posts: 197
Likes: 0
From: West Jordan Utah
I just had a similar deal except I got a p0300 once then 2 p0306 witch is a misfire I pulled the pcv system from the valve covers and plugged off the holes on the pcv and the valve covers and pulled the oil dip stick and found a strong vacuum witch indicates a leak in the intake. Might be a cheap easy way for you to test.
Le Mans Master
Joined: Jul 2002
Posts: 7,370
Likes: 8
From: Slave to the evil empire
Cruise-In V Veteran
St. Jude Donor '04
Thread Starter
Drifting
Joined: Mar 2006
Posts: 1,872
Likes: 7
From: Richmond VA
How about low voltage? Battery going bad, alternator, alternator belt slipping, or a short somewhere? I noticed one time with the hood open, the hood light flickered once or twice when the missing began.
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Thread Starter
Drifting
Joined: Mar 2006
Posts: 1,872
Likes: 7
From: Richmond VA
Fixed! The coupler after the MAF must have worked it's way slightly off at the track. It was just a tiny leak, but enough to give me all those problems. Hooked it back up and she revved to 6k smooth as silk!
Every code on the scanner is now perfect.
Thanks for all your suggestions!
Every code on the scanner is now perfect.
Thanks for all your suggestions!
