P0021 engine code still showing I have replaced coil packs spark plugs camshaft sensors throttle body cleaned MAF sensor and car is still billowing smoke and rough idle still giving me a p0300 code any advice how I can tell if my vtc solenoid is stuck or malfunctioning

 

What did the spark plugs look like? P0021 will not cause billowing smoke.

P0021 just means theres a difference in the cam angle the ECM is demanding vs. what it's actually measuring, typical first troubleshoot would be to pull and inspect the cam solenoid for debris stuck in it's screen, or just replacing the solenoid. No reason to change the cam sensors but if you do it MUST be with either the OEM Nissan ones or Hitachi (Hitachi was the OEM manufacturer).

P0300 random misfire could be a lot of things, did all the old spark plugs look good or was there one or more that looked significantly crapped out? Are you 100% sure you got the coil pack harnesses installed in the correct order? It's easy to get them mixed up.

If you got the coil pack harnesses mixed up you can cause a P0021 because the engine keeps trying to stall.

P0021 can also be caused by a blown gallery gasket although it's less common on the DE engine in the V35 chassis. The HR engine in the V36 chassis was a lot more common. Typically it would throw both P0011 and P0021 though.

If you're billowing BLACK smoke that's rich combustion chamber conditions, maybe a stuck injector. If you're billowing BLUE smoke you need to do a compression test, might have blown the rings.

Are there any other codes you're throwing besides P0300 and P0021 ?