P0302 Cylinder Misfire

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.

Hug0

Unfortunatelly, I don´t have a scope. My uncle has really old one, so I went to his place and we checked it there.

I took some videos, but I need to check if they are OK.

I changed coils (#2 to #4 and back) before and there was no change. I also tried create spark between coil with sparkplug and ground. On #2 coil socket, there was pretty nice spark, on #4 socket (same coil and sparkplug used) there was none. #4 coil is now brand new from NGK (there was some chinese piece of sh*t from previous owner).
Should I check this again with scope?

I checked 12V and ground and it was OK. I will double check that.

According to mods, I think that only one electric related is Uprev tune. I tried 3 different maps without any change.

I would like to change signal wire, but I am not sure if I can change it myself.

I checked all grounds I could find and clear them. Wires looks OK, there is no obvious tension (but I know, they still can be damaged).

SonicVQ

If you haven't already, disconnect the ECU and the ignition coil #4. Check the resistance between #4 signal wire and ground. It should be open.

I think the next step would be to temporarily run a wire from the ECU to the signal wire on the ignition coil.

Use the factory shop manual to find the location of the cylinder #4 ignition coil wire. On my 2011 G37 it is pin #11 and the wire is green. The 370 might be the same or different.


At the ECU tap into the #4 coil wire and run it to the signal wire on #4 ignition coil. Since this is just a test, make it easy for yourself and run the wire out the window to the engine.

** Make sure to use a wire that is about as thick as what is already there. **

The point of the test is to have a known good wire between the ECU and ignition coil #4 signal wire.

• Test for spark strength (like you did before) and compare it to #2 or #6
• Start the engine and check to see if it is running on all 6 cylinders.

I wish you luck and let me know the results.

Hug0

Hi, little update...

It is open.. No shortage there.

If I connect wire to ECU socket with needle or something, there is no change.
Unfortunatelly, I don´t have that small pins to change whole wire without damaging original one.

I don´t want to cut original wire.
Unfortunatelly I can´t find that small pins anywhere.

Btw: we tried to check voltage with scope by putting needle into ECU socket and there was also only 2V.

I will let you know results after I´ll find correct pins and do a proper test with new wire.