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radensb · 01-25-2025, 09:09 PM

I think that's essentially where I'm at. I just put in new spark plugs cuz they have never been replaced to see if that has any effect on the P0300.
It did not.

However, The behavior is still consistent as before so I know that the plugs were not contributing. When I started the engine, it fired right up and ran super smooth. I let it run for several minutes until it warmed up and dropped idle to ~650RMP. Kept checking for codes but none ever popped up. It wasn't until I let the engine warm up and restarted it so that the phasers move to the position (as shown in my last post in the video) did the engine start to feel a bit rough. The roughness corresponded to the phaser adjustment, then smoothed back out when they went back and P0011 and P0300 popped up. To me, this indicates:

The ECU is commanding the VVT, but the system isn't doing what is expected and things get rough, so it adjusts and throws the corresponding codes.
The random misfire is related to the timing adjustments as P0300 was not popping up during the warmup
This means that the plugs and coil packs are good. Otherwise, P0300 would have come up during warmup
Visual inspection is the next step - time to order parts and crack into the timing cover.

The way I am rationalizing this (because I have no other choice...) is that the gallery gaskets are highly suspect being an early '09 and probably need to be addressed anyway. With that justification, its really not much of a leap to justify the additional work and money to replace the phasers an timing chain/components too and leave no stone unturned under there. I can also contribute extra data points to the phaser discussions with my results.

01-25-2025, 09:09 PM	#12 (permalink)
radensb Base Member Join Date: Jan 2014 Location: California Posts: 156 Drives: 09 Nissan 370Z GM M6 Rep Power: 6722	I think that's essentially where I'm at. I just put in new spark plugs cuz they have never been replaced to see if that has any effect on the P0300. It did not. However, The behavior is still consistent as before so I know that the plugs were not contributing. When I started the engine, it fired right up and ran super smooth. I let it run for several minutes until it warmed up and dropped idle to ~650RMP. Kept checking for codes but none ever popped up. It wasn't until I let the engine warm up and restarted it so that the phasers move to the position (as shown in my last post in the video) did the engine start to feel a bit rough. The roughness corresponded to the phaser adjustment, then smoothed back out when they went back and P0011 and P0300 popped up. To me, this indicates: The ECU is commanding the VVT, but the system isn't doing what is expected and things get rough, so it adjusts and throws the corresponding codes. The random misfire is related to the timing adjustments as P0300 was not popping up during the warmup This means that the plugs and coil packs are good. Otherwise, P0300 would have come up during warmup Visual inspection is the next step - time to order parts and crack into the timing cover. The way I am rationalizing this (because I have no other choice...) is that the gallery gaskets are highly suspect being an early '09 and probably need to be addressed anyway. With that justification, its really not much of a leap to justify the additional work and money to replace the phasers an timing chain/components too and leave no stone unturned under there. I can also contribute extra data points to the phaser discussions with my results.