Something to keep in mind with misfire DTC's: Data from the crankshaft position sensor, and the camshaft position sensor data is used by the PCM to detect & accurately identify cylinder misfire. If the crankshaft position sensor relearn data in the PCM, and or the camshaft retard adjustment are not correct, the cylinder indicated by the DTC might be incorrect. With the amount of work involved in repairing the valve guide, it might be in your best interest to have the relearn performed, and make sure camshaft retard is within specs BEFORE you take anything apart.


Switching to a 5W20 full synthetic oil might help the valve stem rotate more freely in the guide. If the valve has not been rotating for a while, (stuck in the same position) it may have started to burn the face of the valve, or the valve seat, in either case, it's time to pull the heads.

 

As an FYI, so I'm not "that guy" for people searching for the problem in the future!

I have not had a chance to pull the valve cover or check the valve, however I did have the O2 sensor on that bank throwing a heating element code at random. I replaced it with a new ACDelco sensor (it was Denso... after market?) and did a foot to the floor on ramp run just like was throwing a code EVERY time before..... no misfires recorded at all! I know it works, if I pull a plug wire and watch, it sees misfires, but it does seem like it may have been a lazy O2 sensor?

I am moving to a new problem for now that I'll make a separate thread on since its likely not related, if this problem pops up again though, I'll be back here and continue to troubleshoot and document the problem.

Now to go ask what lines I need to pull off and clear charcoal bits out of so I can put gas in my tank without taking 10 minutes at the pump...

 

Chuck, how about the old cylinder leak down test? To isolate this issue? Remember the fluctuations I was having with the vacuum gauge hooked up? Wouldn't this be easier and also a quicker way for him to 'find' his problem.....??: also how about the 'high' reading we were getting from the mass air flow sensor???? I suppose there is more than one way to cut the cake??

 

Camera would give a good visual. Both tests could be conclusive.