Smoke test to make sure it's not just a slight vacuum leak. Had something similar on one of mine, never threw codes for misfire but had a weird stumble only at idle (more noticeable with the ac running) and tracked it down to a small vacuum leak either on the intake manifold or the brake booster port on the top of the intake by the pvc.

 

I found a broken air injection vacuum solenoid that I discovered when I was putting the coils back on. Got a new one on order. Could that be it?

Don’t the wires for one bank span across two coils? If so how could it be one coil if if a whole bank is misfiring?

Alternatively, if it was a vacuum leak, wouldn’t that impact all cylinders?

 

Depends on the break in the solenoid. Would it create an air leak into the intake?

Yes! Good point. Each coil pack splits the banks, 2 & 2. I never bothered to look it up but that about rules out a bad coil pack affecting one side of the engine versus the other IMO.



Depends on the vacuum leak. If it goes into the plenum then it would be unlikely to show up on one side only. If it's between the plenum and the manifold then it could only affect the cylinders closest to the leak.

Logic still says that your 02 sensor behavior is pointing towards something else IMO but perhaps not. You have a bunch of stuff to try at least.

 

whowa004 - From where would you do a smoke test? Brake booster vacuum hose or somewhere else?

 

Misfires only on bank 2 since Dec? I'll stand by what I said, process of elimination, and new parts don't do that because they are unknowns. You can get a misfire due to be a cylinder being lean, but not a whole bank without a fuel trim code or oxygen sensor code. One lean cylinder will cause the bank to go lean, and the o2's will tell the injectors to compensate, meaning two or three will be rich and one or two will be lean. 4 misfires on one bank is most likely spark or compression. Lean on one bank due to a vacuum leak will cause a fuel trim code or oxygen sensor code.

Eliminate bad components first,.
swap plugs left to right - eliminate those.
Swap wires left to right - eliminate those
Swap coils left to right - if the coils are bad they will move from evens to odds.
After that, check the rocker shafts.

 

Thanks Extinct. Will report back what I find out.

 

I think I will go ahead and close this one out. I’ve had no errors in a about a week. The only thing I did since I replaced the coils is to clear the unconfirmed misfires, replace the broken intake solenoid and replace the passenger side O2 sensor. I also did a smoke test and found no vacuum leaks.

Still too early to tell for sure but I am leaving for Moab on Friday so I ran out of time to do additional diagnostics.

So for now I will drive it as is and hope that maybe I just needed to clear the codes