P0308 Troubleshooting.

[99Vortec]

Drove my Denali about 200 miles with no problems whatsoever. The next day, I started it and went to talk to a neighbor for a few minutes while it warmed up.

Look over and see it smoking out the tailpipe.

Check engine light was on and showed a P0308.

So I first check the #8 plug and it is drenched like it is not firing at all.

I dry and switch the #8 plug with the #4 plug, hoping the mis-fire moves to cylinder #4. It doesn't.

So I switch The #8 plug wire with the #6 plug wire and the miss still does not move.

So I check for spark at the #8 cap output and it is there. (Although, i am not sure of the consistency of the spark.)

Compression checked out ok for all cylinders.

I noticed that underneath the vehicle passenger side, where the exhaust manifold connects to the exhaust pipe there is oil leaking out and down along the exhaust.

Do I have the #8 injector running non-stop? Or spraying in a jet pattern instead of a fog pattern?

The Spider assembly was replaced about 12K miles ago.

There is no sign of oil fouling on the #8 plug, just raw fuel.

Any Ideas before I have this thing towed in?

 

[Phone Man]

Clogged injector holding it slightly open or its bad.

 

[99Vortec]

Yes. Exactly right. It was a failed #8 injector.



Pic shows raw fuel dripping from the Muffler. Nasty.

This was not an OEM replacement part. Guess I learned an important lesson on using ONLY GM replacement parts.

The spider assembly was less than a year old when it failed.

I'm guessing my Catalytic converter got hammered as well. Anyone?