P0302 Cylinder Misfire

SouthArk370Z

Possibly a wiring problem. FSM (link in my sig) has wiring diagrams and will tell you what kind of signal to look for at the injector. Also lots troubleshooting procedures.

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Capncorroded

With my situation last year I diagnosed it as the ECM. The dealer confirmed it with consult and swapped it out. Luckily I still had a warranty. No problems since.

My theory about why it went "possibly", was error on my part and leaving the key fob in the cup holder during storage. Ive always left the keys in my stored vehicles, and completely forgot about how there is a "wake up" of some features when the fob is in range.

SonicVQ

If you want to troubleshoot the ignition coils, you will need to scope the current of each ignition coil on the primary (low voltage side) typically the coil ground.

When you look at all 6 waveforms, you will quickly find out which one is different and that is the bad one.

If haven't used a scope or don't have access to one, then you might want to take it in to a good shop.

Hug0

Thanks for advices.

SonicVQ:Coils are OK. Also I am 100% sure, that problem is only on cylinder 4.

I tried some troubleshooting. Can somebody tell me what is condenser with connector F8? And where I can find it? I can´t find any pictures of it. I know what it should be, but I cant find it anywhere :/

SonicVQ

The condenser is difficult to find as it is taped to the wiring harness that is under the upper intake.



This is what it looks like:

Attached Images

	1.jpg (208.0 KB, 98 views)
	2.jpg (28.0 KB, 95 views)

Hug0

Thank you!!!!

Little progress: I tried osciloscope today. On cylinders which are OK, there is 5-6V signal on signal wire on coils. On fourth cylinder, there si similar signal, but only 2-2,5V.
Wire from ECM to coil plug seems to be OK (checked with multimeter).

I really hoped, that problem is caused by bad wire, but It kinda looks like ECM problem

Should I try to change signal wire from ECM to coil? According to my uncle (electrician) wire is 99% OK.

SonicVQ

Now that you have a scope, I think the next step is determine bad coil, vs bad wire/ecu.

Set up the scope and get a screen capture (use phone if there isn't a built in function) of cylinder #4 signal wire and either #2 or #6 ignition coil.

Move ignition coil #4 to #2 or #6, and take screen shots again.

Compare the pictures and see if the lower voltage signal wire moves to #2 or #6 or stays on #4. (posting the pictures would also be helpful to me)

• If the low voltage signal moves with the coil, I would suspect a bad coil.
•*If the low voltage signal stays on cylinder #4:
• check coil ground and 12volt supply

Since the original problem got worse after changing the plugs, I would focus on the wiring and check connectors for burnt or bent pins.

When checking wire resistance, it is important to keep in mind that the meter uses a very small current for the resistance test. The ignition coils uses a fairly high amperage of about 12 amps for 0.005 seconds when at idle. (I have scoped my G37's ignition coils)

This can result in the meter showing a good connection, but it may not be a good enough connection for the current draw of the coil.

Additional thought:
Over the years I have tried to help many people with car/engine problems.
About half the time, aftermarket add-ons have directly or indirectly caused the issue.
Melted wires, wires pulled too tight and break internally, loose connections, missing grounds, etc.

With this in mind, please double check any modifications that have been done looking for the items mentioned above.