I searched some threads and can't get the info I'm looking for..
2010 Silverado CCSB 5.3 AFM/DOD engine. 140,000 miles.
P0304 only code. Cylinder 4 misfire.
We have light tapping. Rough idle, no power, stabilitrak and traction control alarms on the dash. Everything I read points to DOD issue with cylinder 4. I have a general understanding of how the system works, but my question is why would the spark plug be oil soaked and misfiring?
A GM tech explained about probable failures with a solenoid in the LOMA, and possible lifter failure if not caught right away, but why a soaked plug?
I did swap plug, plug wire, and coil pack from good working cylinder with no change to cylinder 4 misfire code.

 

The oil soaked plug is a separate issue. Its most likely ingesting oil from the PCV system or there is an issue with the valve seal.

 

Thanks for the reply.
The tech also suggested I remove rocker arm and spin the spring to see if its broken. If it is I guess that could explain the tapping, but would/could it chew up a valve seal?

 

Absolutely! It all depends where it breaks.

 

Will definitely look into that first! Thank you!

 

This was on a neighbors truck. Nearly 200K on the clock when it let go causing a misfire. Bone stock truck. Swapped the broken spring for one from a set of heads that were sent out for porting.

 

I don't think I'm that lucky. I removed valve cover and without loosening a rocker, I can move one on cyl#4 about 1/4" off the valve. I'm assuming busted lifter?
Still not sure why only that plug is oil soaked and not firing.

 

Most likely unless the pushrod is bent. Usually a lifter though...

 

I couldn't upload the short video but it seems pretty obvious the lifter is busted.
Now, take the opportunity to delete DOD, or not delete DOD

 

Delete and be done with it.