2012 Prius, 265k, random misfire, HG or valves?

hi all, ok well here I am again... let's start with vehicle stats; I have a 2012 Prius with 265k on it, I got it at 145k for what it's worth. I replace engine oil every 5k miles, and EGR circuit was last cleaned about 35k miles back (that was the second time for EGR clean out, it has barely built back up the second time around though...).


a couple weeks back I was driving on a freeway feeder and thought I had a flat due to a weird sound/feel, pulled over, all tires are fine but the ICE started up and I heard the dreaded clatter of the dampening plate rattling between the engine and transaxle, ugh... I'm thinking finally, HG gone, the time has finally arrived. no overheating but MIL is on and both p0302 and P219a are registered... I get her home and open up to check coils and plugs, I find the second plug from the left (i thought this was cyl2 but it's really cyl3 I find??) was very loose in the tube and the coil and plug have oil on them... I replaced all 4 coils and plugs and tightened everything up and it seemed to run ok after that, both of the initial codes are gone


but, after getting some driving in I start to hear a very low volume catter from the engine, not from cold start but after it's totally warmed up... haven't seen another MIL yet but when watching the $06 readiness monitor live I do see I'm getting some random misfires ... none on cyl2 now, but random ones on cyl2 3 and cyl4. these are not happening often at all, but seem to happen mostly at idle after extended drives... which seems weird to me, if it were HG related wouldn't the misfires stay put and not travel around from cylinder to cylinder?


I did photograph the old plugs as they came out, hoping they might help to diagnose, but they are labeled wrong if the cylinder order is truly 1,3,4,2 and not 1,2,3,4 as I had thought.... I did notice the second plug had wet oil coating the threads (really cyl3?), and the third plug (cyl4?) had white on its electrode? here's my pics, please keep in mind the mislabeling number wise:







this next one is laid out backwards, so 4,3,2,1 (or 2,4,3,1??)



some more detailed shots of single plugs:



















sorry for so many pics, and the apparent misnumbering? if anyone could clarify I'd appreciate it, is it left-to-right 1,2,3,4 or 1,3,4,2? regardless, the pics above are labeled as 1,2,3,4... but can any offer any opinion as to what is going on with my car? I was ready to go ahead and do the HG but the wandering misfire has me really questioning if it is called for...


I was thinking the wet oil on cyl2 (3?) is more indicative of a bad valve stem seal leaking oil from above perhaps? but the rare wandering misfires have me doubting it being HG, and I am loathe to break the head seal of it isn't actually needed.

I should mention, I already have everything needed to do the head gasket on hand... including a Fel-Pro gasket, timing chain kit, etc... any advice would be very welcome all.

 

hi biaco, no they are not... they are from AutoZone, iridium tipped but not original Denso's...

I also wanted to add, I don't have any codes currently being thrown, I'm not getting a P0303 or P0304, I am just seeing the misfires register as I monitor the "readiness monitor"... I guess the threshold for throwing the actual codes hasn't been reached?

I am torn between just tearing into it and holding off, considering the mileage and such... I should add temps are totally normal, usually topping out at 185f, even being here in steamy houston.

 

hey, thank you for clarifying that, I was really getting confused. ok, then my numbers on pics of plugs are accurate then... would you have any opinion as to what is going on from the looks of my old plugs that I posted Tom?