bgoodman

iTrader: (1)

Hello Everyone,

I am currently getting a 'P0300 - Random Misfire' code when driving my G37 Coupe.

The P0300 code appears when:
- Cruising around 3K RPM (Can be in 3/4/5/6 Gears)

When the SES light is blinking, if I accelerate out of the 3K range, the SES will go away (most of the time).

So far, I have replaced the spark plugs @ 94K miles (currently @ 96K).

Any ideas into what could be causing the random code? I don't notice any sputtering or anything else.

My plan was to change the coils, but when I looked at them, they did not look damaged or anything.

Thx!

GoFightNguyen

iTrader: (14)

Are you boosted?

What mods do you have on the car? I've seen that code on almost every boosted 370 I've ever seen, and even one or two that have pretty much maxed out NA power.

Generally, for them it isn't an issue. The error code is shown if you get one misfire in a certain number of attempted ignitions. The number is large, if you're actually misfiring regularly, you'll feel it.

bgoodman

iTrader: (1)

No, I'm not boosted. The only mods I have is a MXP Catback Exhaust, and Stillen G3 CAI, so I was quite surprised to see it's misfiring... esp. seeing that I'm not feeling it.

Black Betty

iTrader: (60)

I had it. If you sit in a quiet place with the engine idling, you may notice a slight stumble every few minutes. It's very slight and you have to be sitting still and quiet to notice. I got that code on my wife's 09 6MT sedan when the rear timing cover gasket failed inside the engine and caused an internal oil leak. After a while it also displayed P0524 code. It eventually went into limp mode (you can reset it and drive a couple hundred more miles). Have an oil pressure test performed. If pressure is low, that's probably your issue. Hopefully you will be looked upon favorably and your dealership or Infiniti will help you out with the cost. They told me to go kick rocks and mine was at about 80K miles. It's not cheap.

Good luck!

bgoodman

iTrader: (1)

Ugh... I'm hoping that is not the case. If that is the case... is it a repair that is DIY worthy?

Betty - any input on what it could be 'if' the oil pressure is normal?

Black Betty

iTrader: (60)

Not a DIY repair unless you have crazy mad skillz and a lot of time on your hands. Can it be done? Yes. But it is very involved and time consuming. Not a weekend project.

If you have normal oil pressure I'd test each of the coils next.

bgoodman

iTrader: (1)

Thanks! Guess I'll have to drop it off at the dealership to get the oil pressure test.

What would be considered normal for the oil pressure?

Black Betty

iTrader: (60)

I don't recall exactly, but I think maybe about 30 PSI at idle and 60 PSI under load? i also don't recall how low the pressure was. Sorry, I don't have the paperwork with me at work.

bgoodman

iTrader: (1)

Thx for the input BlackBetty. I was able to verify it wasn't the issue you spoke of.

I reviewed all of the connectors in my engine pay and ensured all were tight, and recleaned my MAF's very very thoroughly. Been around 400 miles since without anymore P0300 issues.

Thanks for you and Nguyens help!

bgoodman

iTrader: (1)

*Update* - Over 500 miles since I re-tightened my hoses and cleaned my MAF. No SES lights at all during the past 12 days.

While driving to work this morning, the SES light blinked a few times, but never stayed on. I ran my codes, and it still had the P0300 but no solid SES light.

BlackBetty, do you think it could still be related to the problem you stated... or could the hoses loosened, or MAF gotten dirty again?

Black Betty

iTrader: (60)

Don't know. Did you reset it or did it go off on its own? If you reset it, it will stay off for several hundred miles before returning. If you have checked thoroughly for vacuum leaks, then I'd check each ignition coil next to make sure one of them isn't the problem. Then the oil pressure test.

bgoodman

iTrader: (1)

Yes, I reset it. Before I tightened my hoses, after a Ecu reset, the ses would come on immediately after if I drove it on the hwy.

For the coils, what would be the most optimal way of verifying each one? I read of a few ways, but would rather verify first.

Thanks

Black Betty

iTrader: (60)

Remove them one at a time and test them. Remove coil and plug. Put a new (extra) plug in the hole. Place original spark plug (still connected to coil) somewhere that the plug thread touches metal in the engine bay to ground it. Turn the engine over. You should see a blue spark jump between the center electrode and ground electrode. That means the coil and plug are good. No spark or orange spark means it's bad. Obviously, DO NOT touch the plug while turning the engine over unless you are using an insulated tool. Repeat for all 6 coils.

Also not if there is any oil on the plug when you remove it or any oil pooled in the plug hole. This was a big problem on the VQ35HR engines, but I haven't heard of it on ours. But since you'll have the plugs out, check anyway.

bgoodman

iTrader: (1)

Hey Guys,

I am still having the issue as before, but got it down to a good cadence to when the issue happens. The P0300 code appears after of driving for (30) minutes, before it did it sporadically, but after making the repairs below, it only shows after 30 mins of driving. Any ideas?

So far I have done:

Changed Plugs
Tested all coils (all were good)
Changed a leaky PCV Value (changed both just to be safe)
Replaced all (4) crankcase hoses (used Z1 hoses)
Re-Tightened all G3 pieces and hoses to be safe.

Someone told me it could be the battery going bad or a loose 02 sensor?

thx,

Brian

G37Xtreme

What about your injectors? Did you check for air intake leaks?