Engine misfire on no.7.

Larry Cooke · October 20, 2020

M

Need help. I have a 2015 6.2 that's throwing a Po307 code. Misfire on #7.swapped out the coil, spark plug, and wire with cyl.3. Erased code on startup immediately set code again. Any thoughts on what's next. BTW it does have 103000 miles on the clock. TIA

bdbake01 · October 20, 2020

Better check that exhaust valve spring, like, now.

14burrito · October 20, 2020

Following

Been chasing excessive mode 6 counts in cylinder 7 myself (no codes stored).

CamGTP · October 21, 2020

Broken valve spring or bad AFM lifter are my guesses.

Tucker · October 21, 2020

My bet is a lifter. Been there done that unfortunately.

JONBLARC7 · October 21, 2020

Had the same thing on my L86 at 125K miles. Miss on number 7 it was a bad lifter. Now I have a stage 2 TSP cam and DOD delete because of it. :thumbs: :driving:

I also had a miss on #5 at 115K miles. That was a broken valve spring but It didn't drop the valve so it was a cheap and easy fix.

Don't drive it anymore and pull the valve cover off of the drivers side NOW. It's easy to do. Lets know if you have any questions about it.

Larry Cooke · October 21, 2020

Thanks again for all your help. I'll get it in the shop tomorrow and pull the valve cover. I'll let you know what I find.

14burrito · October 21, 2020

2 hours ago, Larry Cooke said:

Thanks again for all your help. I'll get it in the shop tomorrow and pull the valve cover. I'll let you know what I find.

Did you do any misfire tracking leading up to this, or was it basically hard fault stored and now you are looking into it?

Thanks

evad · October 21, 2020

i had a misfire code on a 12 siverado a 14 taho and a 19 tahoe and all three were an electrical issue .. bad pin connector or green crusty broken wires in the injector or coil harness