2016 SPA xc90 T6 Misfire

[chittychittybangbang]

130k miles.

Sent vehicle to Indy to take care of a power steering problem. Vehicle was there maybe 2 weeks (sat around), and then test driven / repaired etc. Prior to sending vehicle, also had a squeal from engine bay. Saw that the PCV diaphragm was torn, replaced PCV & breather.

While at indy, they asked if I wanted to do plugs / coils / filters.Last time these were done was around 80k miles when Dealer rebuilt the motor due to the piston ring oil burn issue under warranty. I said no.

Anyway, 3-4 days after getting the car back, car starts misfiring. Noticeable rumble / misbalance / limp mode etc. OBD said Cyl4 misfire. I replaced coils and plugs, and it ran well on a cold evening, and then started misfiring again the warmer day after. Then I ran Techron through the system. The subaru rumble is gone, but the CEL will come on from time to time - after about 40 minutes of test driving yesterday for example, the CEL came back on again when my wife took the vehicle out.

I think it may be single injector related - since the plugs and coils are new, and scoping the cylinders didn't yield anything problematic (was looking for vertical scoring on cylinder walls or holes in pistons). Or maybe fuel related, and the injector cleaner helped with a bit of octane boost or something. I kind of hope another bottle of injector cleaner will just take care of it. Maybe it is a valvetrain issue not sure best way to diagnose.

I don't think it's compression because that would result in a cylinder not firing at all, all the time.

Any other known misfire issues to address? Did the 2-ish weeks of mostly sitting around at the Indy cause something to get funky? Low batt voltage leads to random low voltage issues? (No low voltage alerts).

Edit, while all I had were Cylinder 4 issues throughout the last few days while diagnosing, today when wife came home, all codes were for Cylinder 3.

[xiaofei204716]

Remove the ignition coil and spark plug, which may be the problem of the fuel nozzle, it is recommended to replace.
Have a nice day.

[chittychittybangbang]

Hi, can you explain that again? Didn't follow, sorry.