I have a 350z w/ STS turbo kit that has been running fine the past few years. However, a few weeks ago, I noticed my car to make more exhaust popping sounds. The p0300 was being thrown more frequently, but the car sounded and drove like normal. I assumed that the car was running richer and planned to have a retune soon. However, 3 days ago, I noticed the CEL light to flash constantly while casual driving . There was an abrupt change in the performance and sound of the car. It felt very sluggish, sounding like a WRX type motor. Idle is normal and remains constant, and there is no smoke coming out of the exhaust. The car is very sluggish though, and the CEL light constantly blinks while driving.

My car gave a p0306 code, indicating misfire on cylinder 6. I swapped the ignition coil packs with another set I had from a different motor, and changed all the spark plugs with new ones. However, the issue is still there and there are no improvements. After letting the car run for 30 mins or so with the new spark plugs, I pulled them out and saw that all the spark plugs were black except the cylinder 6 plug. The cylinder 6 plug remains clean and not dark like the others. A swapped cylinder 6 with a different coil pack and the issue is still there. What could be going on? Is the ignition bad on cylinder 6 or is the cylinder 6 injector stuck open? Why is the spark plug in cylinder 6 not black like the rest? Thanks

Cylinder 6 plug is first on left below


Cylinder 6 plug is first on right below

 

Take the spark plug out of the car and see if it's sparking, If it is, move on to your fuel injectors.

 

Do a compression check. Very rarely are injectors the source of major issues like this.

 

Tested the ignition coils and they are all sparking. Could this be a ground or wiring/ecu related issue? Not sure it was coincidental, but the problem happened the day after I had my Viper 5901 remote start alarm installed. Had the alarm removed, but the issue is still there. So I am not sure if it is a result of the install or coincidence. The car did feel like it was running richer with more p0300 codes thrown before the alarm install. It just became a lot worst after, with constant misfire.

 

Go through this check list from top down to eliminate all possible variables for this issue.

- Check for intake air leaks. (This can be an issue but more so for P0300)

- Check or change Spark Plug 6

- Check for Faulty ignition coil 6
Ignition 6 harness is exposed or shorted.
Ignition 6 circuit has poor electrical connection.

- Check cylinder 6 for insufficient compression.

- Check for insufficient fuel pressure.
Clogged or Faulty fuel injector.
Fuel injector 6 harness is exposed or shorted.
Fuel injector 6 circuit has poor electrical connection.
Check fuel filter
Check fuel pump

If this were a P0300 which is a Random/Multiple Cylinder Misfire I would have checked all of the above for all cylinders plus your Battery. Yes, a bad battery can cause this even if it's able to start your car.

Hope this check list helps you find the problem.

 

Did a compression checked this morning. The compression of each cylinder were all 180-184. I was quite relieved. This afternoon I will check all the wiring and pull the injectors to have them tested. I am still unsure why the spark plug on cylinder #6 remains drastically clean when compared to the other 5. I tested the #6 coil pack and the spark was good. Could this be due to a clogged or malfunctioning injector on #6?

 

You said you installed a remote start, did you perhaps try to tap into the #6 injector wire for the RPM input?

 

Well by process of elmination all that is left is your fuel injectors.

 

The cylinder isn't firing and if its getting spark the most likely cause would be either that the injector is bad or that it isn't getting a signal from the ECU.

 

im having the same problem with my 07 z replaced coil,plugs and wires and still having same problem car throws out a P0306 and P0024 code

 

Hey skn5002 What ended up being the solution to your problem? I've been dealing with the same thing on cylinder #4 for a very long time and can't drive the car. I've pulled the spark plug and it's visually sparking. I'm checking compression next weekend. I tested the injectors last year and all seemed to check out okay by the multimeter and heard each clicking with the stethiscope.

 

did u ever figure out ur issue? i am having the same exact one on my Z i just bought.