Cyl 6 misfire 40-50mph, no code, slight oil on plug

I got a new-to-me 07 4.0 V6 a year ago with about 180k. Plugs hadn't been changed in who knows how long and misfired badly on uphills. Prev owner told me coils were changed a year prior (2yr old now) with Densos. I put in new OEM copper Denso plugs and it fixed it right up. Been driving it for the past year with no other issues.

It's been a year now and I am getting more frequent misfires on cylinder 6 around 40-50mph. Shows up on slight uphill grades if I'm in 5th, have to brake and try to speed back up. Seems to be eliminated if I pop it over to 4th overdrive.

I verified this is a misfire and not transmission related since I have a bluetooth OBDII reader which counts cylinder misfires while driving even though no code is thrown.

On my trip home today from the shore (4hr drive) I accumulated about 27 misfires on cylinder 6. Idle and cruising at highway speed no issues.

When I got home I pulled the plug and noticed a little bit of oil around half of the edge of the plug, but it wasn't super oily--only one side. Perhaps oil seals need replaced...but would that even cause this misfire or is it probable it's unrelated? I swapped the coil pack from #5 and #6 to see if the problem follows and will report back tomorrow after my commute.

I was initially suspecting injectors since I haven't touched them and there's no maintenance record of them ever being changed...but it's suspect/unlikely since it's mostly tied to one cylinder. I get an errant misfire on another cylinder every once in a blue moon but not common.

Hoping someone with a bit more experience could weigh in..

 

Im pretty sure that oil is external, leaking valve cover gasket / tube seals....
Cool to know toyota does misfire count, ford does...

Shouldnt be driving it at all with every occasional misfire, youre wiping out / damaging your cat converter.

 

Electrode looks good, maybe a little wear but oil could just be from valve cover. Doesnt look like its burning oil. My .02cts.

Swap coil location, see if it follows.

 

You might throw a bottle of Techron fuel injector cleaner in it too.

 

I'd like to see the fuel trims on bank 2 when it happens.

Even looking at the LT now, might give you (us) a clue.

 

Good data! Need input!

 

As suggested, Share some more data, swap parts side to side, and post updates. You sound like you really want to fix the issue not mask it.

That's not a lot of misfires so it may be somewhat hard to track down. It's not throwing codes because there is a threshold for code set criteria.

 

Here is some data for Catalyst damaging misfire, looks like they're suggesting more than 77 per 200 revolutions is considered damaging (CEL blinking). I don't believe 27 misfires in a 4hr drive would be considered damaging.

 

It all adds up and it doesn’t just take a flashing check engine light to cause catalytic converter premature damage…..
What do I know,
Tell that to all these customers in just 1 months time, they thought the same thing…
All customer pay at about $2k+ with labor & then some…
End of the day, it’s a costly part, not worth the risk…

 

This right here actually does kinda confirm it's a torque converter lock-up issue. Some guys have had luck adding LubeGuard

27 misfires in 4 hours? That's nothing. 4 hours is a long time.
That shuddering feeling in 5th, if that was a cylinder misfire you'd see that counter go up to 30-50 in less than 10 seconds. Look at the counter the next time you feel the shuddering in 5th and see if the numbers are climbing rapidly