So I have a 2012 QX56 that has been giving me nothing but problems for about a year now leading up to my current seemingly unfixable problem. I have had a parasitic draw issue for about a year that I haven’t been able to track down that has caused a couple of weird low voltage factory codes when my voltage is under 12.2 so I got better about trickle charging to keep my voltage right. Randomly, I start getting a rough idle out with the family and a blinking CE light, with a scan I’ve got multiple misfires. I let it set for a few days, idle got tougher so I make an appointment to take it in to a shop, get my spark plugs and O2 sensors (160k miles on them) replaced along with my valve cover which cracked removing the bolts for the coils. Still misfiring $2500 later and mechanic tells me to take it to the dealer. All of my misfires are on bank one, most on cylinder 7 (almost continuously) half as many on cylinder 5, and half again as many on cylinder 3. This seems like it has to be an indication of something that I could look into, but I can’t find anything. Begging for help here. The only thing I’ve found is that a lot of people get misfires from the high pressure fuel pump bucket issue (which I’m going to check) but short of this causing fuel starvation on 3,5,7 I don’t understand how it could just be those cylinders. Any thoughts from anyone would be greatly appreciated.

The injector wires for the odd bank all go through the same subharness connector from the engine harness, F60:F121 at the front of the left valve cover. If the problem is electrical, those connectors and the subharness would be likely candidates.

Unfortunately the EC and PG sections of the FSM's seem to be missing for the '12~'13, but the '11 is similar and you can find the connector location on PG-148 here:
https://www.nicoclub.com/service-manual ... 1%2FPG.pdf

I know it's a PITA, but it might be worth your while to pull the plugs on that side and check the burns, and run a compression test if they look suspicious. For whatever reason, when VK56's scrub-out cylinders, it's almost always 7 or 8 first and then progressing up the bank. If you have a black or oily burn on the suspect cylinders then a wet/dry compression test is definitely in order. Likewise, inspecting the plugs will also tell you if it's fuel starvation, lean running causes plugs to run hot with a white burn instead of chocolate.

I pulled plug 5 and it’s black and wet, 7 is a task for while the mosquitos are away. I will definitely try to locate that wire loom tomorrow and hopefully find a problem there as I don’t know what you mean when you say “scrubbed out cylinder” but that sounds like a very very bad thing. I’m assuming I can grab the specs for a compression test from the engine section of the 2011 FSM without too many worries? I pulled the high pressure fuel pump and everything there was spotless btw

"Scrubbed out" means the rings are shot and the cylinder walls are scored or worn out. Your inkling is correct, it's very bad. Yes, the compression specs for '11 and '12 should be identical. Was the "wet" on the plug fuel or oil? If you're uncertain, leave it out overnight. If it's oil it will still look wet in the morning, if it's fuel it will dry out.

I hope there’s a better news answer than that… How common is ring failure on these engines. 165k seems too damn soon…

Not all that common, but when they do scrub out, it almost always starts at 7 or 8. That's why I'm suspicious.

Is this also a common place for a head gasket to go out? I did have an overheat about a month before all of my problems started when my rear coolant line burst. I’m just trying to think of something that doesn’t involve trashing the engine/car. I’m gonna go buy a compression tester from Harbor freight as the rentals I can get don’t fit the tiny a** plugs in these things and I also have a camera that I might be able to get inside there to look at the cylinder wall.

Head gaskets on any engine can pop from an overheat. If you're going to scope the bores, a head gasket is easy to spot. The piston crowns and valves will be shiny from the coolant blowing the carbon off them.

The plot further thickens, did a combustion leak detection on it, no leak detected, did a compression the only cylinder that was more than 5 psi off every other cylinder was cylinder one, still well within 10%. As a fun throw in there was oil in #3 meaning the valve covers that ai just spent way too much money to have installed have to come off again…. Also they didn’t gap my plugs, they just said close enough as they were all off by .001-.005 The wetness on the plugs turned out to be gas, dried out quick while doing the compression test.

Your ride has push-pull injectors, so pretty much the only way a cylinder can flood with fuel is a mechanically stuck injector or a lack of ignition. "Rich" would just make it crappy and sooty but not wet. So that actually eliminates a lot of stuff.

So what do I have left to check, I’ve swapped coils from the other side, misfire doesn’t move, so at this point, I can check the resistance on the connectors to see if there’s any difference, ohm out the plug to ground and at that point it’s pull the ecm time?

I'd start with a flash test on one of the coils to see if the spark is strong, and if it's weak do a voltage drop test on the coil power to #7 and the grounds on all four. If you exclude the coils and coil wiring then the injectors are pretty much all that's left.

So, never trust a mechanic… this mf’er said he swapped the coils side to side when he put it back together. Well no the F he did not. When ai went back together I of course had numbered all of my coils so I swapped all of my plugs and coils and guess who now has a very slight misfire on 8… I have a weak coil that was either not properly connected or mixed with an improperly gapped plug was acting up. No ce light no dancing motor, nothing. Six f’ing weeks I’ve been playing with this thing avoiding the dealer and it comes down to a weak coil. I still have to pull the cover and replace the seal on coil 5 that must have been bad from the factory as it was pre installed on the oem cover, and that jobs gonna suck, but other than that, I think my nightmare might be over.

I back traced all my lines to the ecm and ohm’d them out, checked all my body grounds cleaned out all my connections with electronic cleaner and it was all because my mechanic was full of s***…. However, you unlike my mechanic are the greatest person ever. Thank you so much for all of your help! I know it kind of resolved itself, but without you giving me direction and things to look for, I never would have done that compression test which gave me the opportunity to swap my coils. You are the friggin man dude thank you so much for having a response to every post and quick ones at that. Can’t begin to tell you how appreciative I am.

Pay it forward, son, that's all I'm doing. But, I do need to point out, you are trusting a mechanic.

Jk. If I wasn't one, I'd be royally peeved at that guy too. Or maybe I'm more peeved, I dunno. I have little patience for people who dishonor the profession.

In any case, happy to help and glad your ride is on the road to health. Happy motoring!

Lololol so I was able to hear a rubbing sound in the wheel well that wasn’t there previously so I got out to take a look and saw that when he pulled out the plastic guards in the wheel well to replace my o2 sensors (for which he charged me $190 labor) he never put them back in…. I can see my ignition coils through the wheel well. The situation sucks because I can’t even talk s*** about him because he’s a client at my work and my boss is a lunatic.