MY350Z.COM - Nissan 350Z and 370Z Forum Discussion - 0300 misfire solved, sharing my experience.

This misfire happened a couple of months to my 350Z 2003 touring with standard transmision.
So we went to a ride sightseeing, car was great that day and performed ok.

My mistake, I almost used all the gas in the fuel tank, went to the reserve,
A couple of days later the car felt wrong, you could feel rattling and maybe a mild misfire, no check engine. Intermitent. I had to pass emissions and it worked well and passed, but when riding home the car got the check engine light blinking and could feel lack of power and missfire.
Took it home , learn how to retrieve codes and found out that I had a problem with the heating element of the O2 sensor bank 2 upstream.
So diagnostics started, I pulled the sensor conector, checked it with multimeter and was ok. Couple of days later 0300 intermitent misfire.
Continued diagnostics, first erasing codes. Then went for a ride and check engine blinking now with 0301, this was good news, I knew where to look for a fault.

I took the fuel pump out dissasemble it and cleaned with ultrasound, it was not that dirty but some debris in the filtering element that looks like a sock.

Checked for vaccum leaks with propane , no problems there.

With the engine running dissconected the ignition coils one at a time, no problem. Checked the wiring and power and ground ok. No way to check for signal. Then I took a spark plug put it in ignition coil ground it and checked positive for spark. Checked spark plugs and only #1 was fouled. Cleaned it. Reasembled and drove for a while. Check engine light would sometimes come on and dissapear until it was on steady all the time.

Removed plenum, cleaned some oil inside and went straight to the injectors. Cleaned by ultrasound and checked ohms also activated them and all was fine. wiring was ok apparently.
Assembled again, test drive and the car worked fine for a while and missfire again.
I bought a scanner, a Launch CRP123 or something like that. It gave me some info on fuel trim, O2 sensors working and help me understand how the car was working when missfire happened.
It was weir because trouble started even when cold at idle, but sometimes until I hit 3000rpms.

I then went to the Nissan dealer for them to fix it,
I was giving up.
But I wanted them to make diagnostics with lab scope and scanner. Not throw parts randomly because that , I could do and it was really expensive. They could not do that because their scanner was stolen. So back to my house, limp mode, scared to damage the catalitic converters that here cost around 2000 usdlls each, ! I have read that a rich mixture can damage these very easily.

So I started again. Went to the lab to check the inyectors for flow, leakage, and function. Everything fine. So I changed inyector 1 to the #3 position, and Ignition coil 1 to the #2 position because I was having a 0301 code. Erased trouble codes and drove. Check engine again! Scanner told me in number 2 cilinder so this time I knew it was the ignition coil.
Bought one Hitachi coil from Amazon and just installed it. Car works great for now, no misfire, no check engine . Just fine.

So I wrote my experience because I wanted to share something that I can not figure out yet.
I checked the Ignition coil a lot of times, disconected one at a time and rpm dropped each time usually. Checked the wiring and everything ok on power and ground, signal was moving when I checked with the multimiter that is supposed to not work for this. I checked ohms in the primary wiring from the ignition coil and was ok. And the Ignition coil works producing a spark!!
So how can one know when the coil fails even if it works??

Hope this is usefull to someone. Sorry for my rusty english, not my native language.