P0300 Nissan - missfire and smells rich

Question

I just changed the spark plugs and intake gasket seems to be good. Coils a 2 month old. Maf is new.
Should I put new intake gasket? If so wich one ? The middle one or both? And can a vacuum leak cause a random missfire?

Answer 1

Yes a vacuum (intake) leak can cause a random misfire

bad injector/s may also cause a p0300 or bad ignition coil/s

also a bad fuel pump 

p0300 is hard to diagnose, unless you know what to look for next 

 

 

Possible causes

- Faulty spark plug (s) 

- Faulty ignition coil (s) 

- Clogged or faulty fuel injector (s)

- Intake air leak

- Fuel injectors harness is open or shorted

- Fuel Injectors circuit poor electrical connection

- Ignition coils harness is open or shorted

- Ignition coils circuit poor electrical connection

- Insufficient cylinders compression

- Incorrect fuel pressure