P0300 Troubleshooting

[LukeK]

Car: Nissan Navara D40 ST-X V6 Petrol 2007 (Spanish model)

Error code: P0300 (random/multiple misfires)

So, my car out of nowhere kind of hit limp mode. It's got no balls when you accelerate, and makes a loud sound it didn't before. Scanning it (both me and a mechanic) it's only coming up with P0300 code.

So far I have
Changed the spark plugs
Changed the coils
Changed the maf season
Changed both the cam angle sensors
Changed the crankshaft sensor
Changed both the vvt solenoids
Checked the cats (they're near on spotless)
Ran a multimeter on the 02 sensors and they were fine, one was dirty so I cleaned it
Been checked for air leaks

I've been told the timing sounds a little bit off, like whatever is wrong may be effecting it. I can put the accelerator to the floor and it just has no pick up.

I'm kind of out of ideas on what to possibly check now. Feel like im getting nowhere.
I mean with everything I've changed it idles and sounds nicer at least haha.

But it's not currently drivable how it is.

 

[Old.Tony]

Ok, the manual covers this one in a little detail. 0300 is a multiple cylinder misfire (0301 is misfire on cyl 1, through to 0306 on cyl 6). I'd be more inclined to look at parts of the system that aren't specific to an individual cylinder because you don't often get two cylinders doing the same error (although that's not impossible so we still need to check).

The manual lists the following possible causes:

* Improper spark plug #
* Insufficient compression
* Incorrect fuel pressure
* Fuel injector circuit open or shorted
* Fuel injector faulty
* Air intake leak #
* Ignition signal circuit open or shorted
* Lack of fuel
* Signal plate (for the crankshaft pos sensor)
* Air fuel ratio sensor 1 fault
* Incorrect PCV hose connection

You've covered a couple of those (marked #), the air intake leak may also be an EGR leak (block it off if you want to test this).

Let's go over the others.

Have you done a dry + wet compression test? I'd look at this one last.

If idle is smooth the ECU is regulating fuel pressure ok at idle but if it's not at throttle demand it might be related to either the throttle assembly, throttle body OR the EGR valve. Start by blocking the EGR.

Inspect all wiring, particularly looking for crush damage on the harness.

How long since you've used a good injector cleaner in the engine? I use and recommend Liqui Moly Fuel System Treatment (works for diesel and petrol engines) and not just because they sponsor the Bathurst 12 Hour!

Is the fuel tank full, and is the fuel contaminated? How fresh is the fuel filter? If you pump a little fuel from the filter intake hose into a clean jar, is there any sign of debris (might have picked up a bad batch of fuel @ servo)?

If you pull the crankshaft position sensor and look inside, do the teeth of the signal plate look clean?

The AFR is related to the MAFS and is used to monitor the oxygen content in the exhaust. If it's a faulty EGR valve there'll be less oxygen in the exhaust and may trigger this sensor so blocking the EGR may resolve this one too.

PCV is supposed to be connected to the air intake between the throttle body and the intake manifold. Make sure it is fitted correctly on both ends, I recall one person reporting that their PCV outlet on the top of the engine was broken!

I've attached EC.PDF which is the Nissan service manual document that manages troubleshooting for the error codes in 2006 to 2010 Navaras with the 4.0L petrol and 2.5L diesel engines. I've also attached EM.PDF which is the mechanical part of the manual and EC.PDF refers to it in the section on your error code.

Are you getting much smoke when putting your foot down on the throttle?