Hello all, I'm new to this forum and wanted to ask about this issue. I originally had my SES light come on about 1 month ago. The code was bank 1 too lean; 1 week later I took in to deal to have all injectors replaced. 1 day after getting car back; my SES light came back on; this time it read 'multiple random misfires'. I was told that this was caused by engine running lean for extended period of time, I didn't buy this however, I was told that replacing the spark plugs,I had replaced 1 1/2 years ago would clear code and correct issue. I allowed them to replace all plugs. Not even 5 days later, my SES light comes back on again with same code! Immediately took back to dealer for them to check. Now the tech believes replacing AF sensor both will correct the readings they give the computer and therefore no cause misfires. The readings on the computer are reading a little lean, but they are still within range he states115.

After reading the threads here related to misfires; it appears the issue is related to a blockage in a cylinder head. I've replaced pretty much everything related to the engine and according to tech; sensors working as expected he even swapped out MAF with new one and same reading; so my guess is that somehow cylinder is blocked even after the work??

she is 2003 G35 sedan 6MT with 188k
no engine issues prior to this and I baby her. I'm actually surprised that I'm having these issues given the fact she's well-maintained. but maybe this is normal.

What do you all think?? Any help would be greatly appreciated!

 

I've never heard of any issues with blockages in the heads on these, and I work on cars for a living, but then again you learn something new every day.

That being said, if you had a blockage in a head that was causing a misfire, I'd be inclined to think that it would cause a misfire for a specific cylinder. It shouldn't cause a random multiple misfire. At the very most it would cause 3 cylinders to misfire on the same side, but one bad head shouldn't cause the other side to misfire necessarily.

Now I do know that nissans in general throw lean codes for bad airflow sensors pretty often. You say they swapped one out and it still did it, so it may not be that, but another option would be to look for a vacuum leak. If it's sucking in air after the sensor, but before (or at) the the intake manifold, then you have unmetered air entering. Which WOULD cause a random multiple condition. If it were a vacuum leak AFTER the intake though, it would affect one side only, not both, as far as the misfire goes.

Have them look at the fuel trim levels. If you have an excessive positive fuel trim, it means the o2s are detecting that it's running lean, so it's dumping more fuel in to compensate. This would also indicate a vacuum leak.

 

Thanks mjw011689!
I was told that there were no leaks; but I'll ask them to check fuel trim levels.
It's been a couple days now and the SES light hasn't come back on yet... (knock on wood).
In the meantime, is there anything I can do to check/look at myself?

 

Guess what.... SES light came on again Sat. So I brought back it right back to dealer (Tue) to have them check; "they were too busy to look and the mechanic whose been working on was off Wed."
Before bringing it in, I noticed A LOT of oil and gunk under the engine on drivers side; to me, there is definitely a leak and something not put back together correctly. Mentioned this to service dept.

I'm done.

Looking into a new vehicle at this point.

Damn shame that mechanics at the dealer DON'T KNOW WHAT THEY DID TO SCREW UP your car! It's suppose to be their specialty! What's worse is they charged me over $2500 to do injectors and spark plugs and car runs worse than when I brought in.

Hoping this can and will help someone out there.

On a side note, this AM SES light went off. Is she telling me something!???