R33 misfire issue?

[r33evosho]

Got a bit of a situation.

Car has suddenly got a misfire.  Car from a cold start has no issue, runs normal etc.  Take it for a short drive after it's warmed up, acts normal and then feel like I lose a cylinder.  Only thing is as you put load on it getting past 3k RPMs, problem is GONE.  Then driving after a few minutes it's fine regardless of rpm.  It's kinda strange.

Original coils, new plugs, BRAND new coil pack harness

Pulled the rear 3 coils and pulled the plugs.. see attached.

Pistons look clean no carbon buildup.

 

[tridentt150v]

Looks lean to me, those plugs look too white.  Probably not your issue - unless your pump is on the way out.

[joshuaho96]

I agree it looks lean, but it doesn't really explain anything. I would try and log the behavior with Nissan Datascan, if you see stuff like MAF randomly dropping out at relatively constant throttle position then that could be the reason why. If MAF looks signal looks halfway decent but you see O2 voltage dropping to 0.2V or less for extended periods of time when the engine is not in DFCO then could be an ignition misfire, but if this is inconsistent I would be more suspect of the fuel system. Could be that the fuel pump isn't flowing enough until the FPCM kicks the fuel pump to full voltage. The O2 sensor starts reading well before the engine hits 80C coolant temp so you should be able to catch the behavior. NDS also has a function where you can disable individual cylinders, if you can reliably reproduce the problem you could get a friend to disable each cylinder in turn when the issue occurs to try and see if you can narrow it down to a specific cylinder, it should lose power/change engine note/rpm any time you disable one cylinder.

To try and make sure that your coilpacks are not the issue I would pull the coilpack bracket + coilpacks out, vacuum the valley thoroughly/remove any debris, then wash the coilpacks thoroughly with soap and water, they're fully potted so this won't cause issues. Dry the coilpacks thoroughly, then apply dielectric grease at the top of the boot near the spring and around where the spark plug ceramic insulator is, then put everything back together. Also make sure that the spark plugs you bought are not counterfeit or otherwise off in some way, I've had suspect spark plugs before and they made the car run ok for the most part but during idle I would feel the idle suddenly dip and the engine would have to open the idle air control valve up to catch the stumble before the engine stalled.

There's a guide out there on verifying the coilpacks more thoroughly but it's a real pain in the neck and involves pulling the CAS out, disabling all injectors, and removing all plugs + coil bracket and putting the spark plugs up in the air to while turning the CAS to see if the spark jumps through a stray path when nominally in a scenario where the spark plug electrode (ground) is not connected and therefore no spark should occur. Kind of dangerous to try though, make sure to discharge the plugs with some kind of insulated wire to the engine head to not shock yourself with like 10+ kV, the current is pretty trivial but it doesn't take much to cause problems with your heart rhythm.

[blind_elk]

S1 / S2 RB25DET? How do you know its 1 of the rear plugs that is misfiring?

I've had similar problem - turned out to be a failing coil pack. Since you still have the OEM coils, suggest you upgrade to new ones.