2005 Altima - P0300 Misfire - Please help.

[VGZ]

Hey Guys,
I have a 2005 Altima SE-r that has a misfire. I decided to try and fix it. From what I read, I was supposed to check the coils, injectors and plugs.
I pulled the intake manifold of, checked the coils for operation and checked resistance, checked injector resistance, checked every spark plug to make sure it sparks, checked coil connectors, checked voltage at injector connectors. Only thing I found was oily residue in the back 3 injector connectors. I will clean them out tomorrow but I am wondering what else this issue can stem from. I have read everything across the board from cam and crank angle sensors to bad 02 sensors to bad MAF etc but I just want to see if anyone has experience with this issue.

The car runs pretty bad. It use to misfire randomly and the code could be erased but came back. Now the misfire is constant and sometimes the CEL flashes which means catalytic converter damage may occur. I smell a moderate amount of fuel from the exhaust when it is running and the idle is rough and hunting. Sometime I smell the sulfur (rotten egg) smell which is the cat. Seems like at least one cylinder is not operating or at least misfiring constantly although the code indicates it is multiple cylinders.

Any help would be greatly appreciated.

[VGZ]

Checked the Camshaft and Crankshaft position sensors today. Ohmed to spec. Also checked the IVT solenoid in the front. Could not reach the one in the rear. Ohmed out fine too. Cleaned the injector connectors but I doubt thats the issue. I have read it can be either the 02 or A/F sensors but diagnosing them is not easy since I don't have consult. Please let me know if you have had any experience with this or have a suggestion.

[QR25DE]

If it's not throwing an o2 code then I wouldn't look at the o2 sensor. The car is pretty good about measuring this sensor voltage and knows when it dips too low/or goes too high.

I would suggest looking at a more hardware related issue than a sensor issue. Sounds like possibly there may be engine damage. Can you make a video of it running?

[VGZ]

Sure, as soon as I re-assemble it I will. Probably this weekend. Not sure why I would have any damage but I will look into it. Maybe a burned exhaust valve or something?

[QR25DE]

Could be, i was kinda leaning that route. Hopefully it's something stupid. Maybe take out all the injectors and have them cleaned? Might be one injector stuck open or something. If you're getting a rotten egg smell that would be too much fuel for sure. It takes A LOT for the car to throw an o2 or too rich code. (I've only done it once for too rich, and right now I drive daily dipping into the mid 10s for AFR at full boost sometimes). I only threw the code once when it got really rich.

A rotten egg smell is from the sulfur, you motor isn't burning the gas and and ur left with a rotten sulfur smell. Too much fuel.

[VGZ]

Could be, i was kinda leaning that route. Hopefully it's something stupid. Maybe take out all the injectors and have them cleaned? Might be one injector stuck open or something. If you're getting a rotten egg smell that would be too much fuel for sure. It takes A LOT for the car to throw an o2 or too rich code. (I've only done it once for too rich, and right now I drive daily dipping into the mid 10s for AFR at full boost sometimes). I only threw the code once when it got really rich.

A rotten egg smell is from the sulfur, you motor isn't burning the gas and and ur left with a rotten sulfur smell. Too much fuel.

Well I really doubt it is one stuck open. They all ohmed perfectly and exactly the same. Also, it would not be multiple/random misfire unless several were stuck open, would it? I was really adamant on the no spark Idea but that obviously did not work out. I could send them out for a sonic cleaning. I guess bad gas could clog a couple of them up. I do not smell the sulfer all the time, just twice but I do smell unburned gas pretty constantly. I thought the sulfer was the cat getting damaged from raw hydrocarbons? I guess I have not been all THAT rich yet since the 02 code has not come up. Would you send out the injectors if you were in my shoes? Thanks for all the help btw.

[QR25DE]

If I checked all that stuff and couldn't fix it I'd take it to Nissan for a diag and then you can fix it yourself if you can. They can track down the issue pretty quickly.

If everything is checking out fine then it may be internal. Try resetting the ECU? (Disconnect it from power for 10 minutes) / unhook battery. That fixed a problem I dealt with in my neon (even after I changed the bad sensor). ECU needed a full restart. Worked like a charm.

Shooting in the dark now though :/

[junejune0605]

Hey, I dont mean to thread jack but I'm having a similar issue.

I just purchased a 2005 SE-R and I've been having an issue with the SES light coming on.

When I did OBD, it gives me P0300 Multiple/Random cylinder misfire.

I took it to the mechanic (which ripped me off $331), he said he checked everything, coils, spark plugs, relays, ect... So he said only thing could be that theres carbon buildup bla bla bla. so he did an induction flush.

Less than 24 hrs later, I get this code (again)...

The way the code starts off, rough idle at light and the SES light will flash. When I start moving the car, it goes away. Same thing at every light until it stays on permanently.

I checked with Nissan and there isn't a camshaft sensor recall.

I'm stumped, and I don't want to continue dishing out $$ without a fix.

Please Help...