I'm getting a P0300 again. I have had these on and off over the years but in the past a quick code clear has banished them for sometimes months but always at least weeks. Now the code comes back almost immediately. No other info - whereas in the past I always got a second P030X code point to a cylinder. The car runs fine - no indication of any problem, and it has plenty of power although I didn't do any dyno testing.

I have replaced all the obvious stuff over the years - using the 6th gen valve covers, all coils, plugs, even parts of the recirculating exhaust system. I will replace the coils and plugs again since it has been a few years and perhaps something has gone wrong. I was thinking about the EGR harness since some people have had problems with the pin connectors but Nissan does not make them anymore. I will still give a detailed look into the connectors but I was also wondering about the injectors which are still original. Not sure where I would even get either part if there is something wrong.

Only reason asking is that car has to go through Cali inspection and it will fail with the SES light on. I will likely just pay the fine and keep going.

Thanks in advance. Any thoughts?

 

No, you can't "just pay the fine and keep going": Your SES light has to be off, and more important, all your monitors must be "completed".
Trust me, I also live in the Bay Area. I have been through all this stuff last year - they did not let me pass with one incomplete monitor until I had it fixed.

From your description, it seems that your injectors and your coils/plugs are worth checking.

I have never replaced/checked my injectors so I can't help much in that area. I have recently replaced my coils&plugs (got p1320); to my surprise, this replacement cleared the P1320 code although the car drove just fine both before and after. This replacement can be done for about $220.- plus 2 hours of your labor.

 

cam or crank sensor probably

 

Po300 can be a number of things. It's usually affecting more than one cylinder. I would start by pulling the coil packs and making sure there is no oil in the holes. I know u said u replaced the valve covers with 6 gens, but I did also and they still leaked just like the 5 gen valve covers to my surprise.

 

Just a follow-up here. My mechanic forced a 302 code so he went and replaced the #2 coil - fault came back. I replaced both cam sensors - fault came back but eventually went off. I was able to get it smogged yesterday and SES is still off so who knows. Got another 2 years to find out. Going to make it tough to decide if replacing the clutch (original) is worth it. Thanks for all the help.

 

Replaced both crank sensors, you mean?

 

While working on that VQ I would clean all the grounds...and install them with star washers

 

Oddly enough the courtesy nissan parts site use crank and cam interchangeably. I replaced the cam shaft sensors (23731-6J90D & AL61D). But now I see there is also a crank shaft sensor which courtesy doesn't seem to have any. Sounds like I should replace that as well (amazon appears to have one).

 

 

Its an 02. The courtesy link is https://www.courtesyparts.com/auto-p...on-system-scat
You can see they list both CAM (#4) and CRANK (#6).