2014 Tahoe SSV - Cyl 6 misfires. Wires & coil swapped, still misfiring.

[tamitall]

Greetings!

Started out with a P0306 code (cylinder 6 misfire), swapped in a new coil, cleared the code, it came right back. Runs rough at idle, but OK (though down on power) at speed.

Swapped 4 and 6's wires, and the code turned into P0300 multiple cylinders misfire. Bought a new set of Edelbrock wires, swapped both 4 and 6 in, and... still P0300 and rough idle.

I'm thinking it might be an injector? Any thoughts on what I'm missing?

Also, new plugs & wires less than 1 month ago.

Thanks!

 

[Foggy]

How did your spark plugs look ???? If you did wires, you prob need plugs too.... If
that's the cause..
It could be a DOD lifter failing (or the VLOM) as well

just read you did plugs a month ago Which plugs did you use and where did
you get them from (yes, it could make a big difference) ??

 

[tamitall]

How did your spark plugs look ???? If you did wires, you prob need plugs too.... If
that's the cause..
It could be a DOD lifter failing (or the VLOM) as well

just read you did plugs a month ago Which plugs did you use and where did
you get them from (yes, it could make a big difference) ??

My local fairly trusted shop did the plugs and wires. iirc. Delco plugs, per their recommendation.

I haven't pulled the new plug, and I didn't see the old ones, but it didn't alarm them.

This went from no check engine light directly to flashing CE and stabilitrack and traction control lights. No buildup to it failing that I could see.

I haven't heard any bad noises along with it running on 7, but I'm curious about the DOD lifter idea too. The engine only has slightly over 106k on it, but well over 10,000 hours. It idled a lot in it's former life.

 

[Foggy]

There have been counterfeit plugs on the market.. But if your shop got them locally then they are more than likely OK
I just went thru a misfire that went from Cyl #2 to a random P0300 after a dod delete cam swap.
It ended up being a bad coil pack - which is very unusual... My engine has about the same mileage as you,
but only 3000 hours.. So it could be a lifter failure you are chasing.
Good luck .. You'll have to pull the valve cover on that side to look at the actual movement of
the rockers on that cylinder.. That would tell you if it's a lifter

 

[tamitall]

The more I've read, the more convinced I am that you hit exactly what happened. I'm going to tear it apart and check on the lifter this weekend. Thanks for the nudge in the right direction!

 

[tamitall]

After watching that video, I'm going to attempt this repair myself.

 

[Foggy]

After watching that video, I'm going to attempt this repair myself.

I did that fix to a friends 09 gmc 5.3 L and it did work.. I just used
a cheap push rod from the parts store.. You'll need a pushrod that is slightly
smaller in diameter from the stock one to fit into the DOD Oil Hole.. I put antisieze on it and had to pull it out with a vice grip, but it did work..
Saying this: he only drove a very short distance from the first "knocking"
noise just to get it home.. If you have driven quite a distance with the
stuck lifter your results may vary