2004 350Z. The car was driven for some time with a misfire condition. It now sounds like it may have an exhaust leak at the driver side manifold and is throwing a P0300 code (Multiple Cylinders Misfiring) and will not rev pats 3500RPM. The CEL also flashes or goes out completely from time to time. What actually happens in the cylinder when it’s misfiring? Does the cylinder load up with fuel? What append to the fuel that’s injected?

Cylinder 6 (driver side firewall) spark plug tube seal is leaking oil and the plug electrode is covered in oil. This is the only bad one as the rest were clean and dry. That coil pack also separated into two pieces when removing it, but it appears they can be taken apart with minimal effort? Not sure if this is part of the misfiring issue in that cylinder but either way that plug is fouled with oil. It was also over gapped at about 0.050.

I’m planning to replace all the coil packs, spark plugs and valve covers to start. Is the sound that appears to be coming from the driver side a leaking manifold gasket or does it just sound like that due to the misfiring? It didn’t sound like this for the majority of the time is was driven while misfiring. Is it possible to blow an exhaust manifold gasket as a result of driving with a misfire condition? What’s the worst that can happen from driving it with a cylinder-specific code?

The driver side exhaust is putting out a lot more white smoke than the passenger side, but thats not an indication of anything going on with that side specifically because it’s not a true dual exhaust, right?

Any help is appreciated because I need to get the car running and inspected or my HOA will tow it Monday.

 

Did resistance check on each coil. Coils 1 and 5 both have Open conditions on pins 2 to 3 and 1 to 3. 1 to 2 reads about 470 Ohms. The rest of the coils get a reading of just under 500 ohms on all pin to pin configurations. Does anyone know what the expected value is for this reading? Is about 500 ohms correct or too high? I swapped out coil 1 with a good used one and the car is running smoother but still misfiring. The bad exhaust noise that sounded like a manifold leak has just about disappeared as well, thank God. Parts will be in Wednesday.

Also, all the plugs look to be fouled from a rich mixture due to a dirty Popcharger filter or the misfiring or both. I cleaned and reoiled the filter.

 

The larger gaps will cause a misfire, that being said, I don't think a misfire could cause a gasket failure. I would check it after the plugs and coils are done.