Fixed P0300 Multi Misfire / Now Have P0302 Cyl 2 misfire

[Wrierblock20]

1998 Nisssan Pathfinder 2WD here, Change the Fuel Filter, Spark Plugs (NKG), Plug Wires (NKG), Distributor. Previously would get P0300 now only get P0302 after changing all parts mentioned above, The Misfire does go away after driving even when already warm now, It takes 1-2 minutes of driving before it goes away though, I Ran fuel system cleaner Gumout FUll tank of gas + Premium Gas, This has not really done much and the tank went near empty today, I have checked for vacuum leaks with Carb Cleaner all around throttle body and vacuum lines no change in idle speeds, The Misfire now is ONLY present after shutting down the engine and letting it sit for at least 5+ Minutes then turning back on then after 1-2 minutes of driving it goes back to normal no misfire, Is this a sign of a leaky Injector? I have confirmed Spark is good, when misfiring i have pulled the Plug for Cyl 2 and it makes zero diff in the way the engine is currently running while misfiring so that confirms Cyl #2 problem but i confirm there IS spark coming from the plug wire for Cyl #2. Currently I am running 10GAL of Regular grade gas (from Chevron) with Royal Purple MAX Injector Cleaner. also on the plus side i have Wayyyy more power, no hesitation after the 1-2 min start and misfire goes away and it starts pretty quick now! Have also not had check engine light flash.

[Wrierblock20]

how do i check the fuel pressure on this engine?.. Do they expect you to cut the return line and test from there!? I see white lines on the rubber hose passenger side.. I Was checking FSM but does not specify to cut them? I have a fuel pressure check gauge with all the adapters rented from autozone, I also squeezed those lines and they were not hard, are they supposed to stay hard after engine is off? Maybe its another sign pointing to fuel injector leakage, also it says disconnect the vacuum hose and check pressure, which vacuum hose?


How would one perform a injector leak test would it be crimp the return hose behind the fuel pressure gauge when installed and then also crimp the feed hose? then if pressure drops quicker than 30min likely fuel injector leak?

[Wrierblock20]

Also can i remove The #2 Injector without removing Intake Plenum, I can see the #2 Injector just behind the Dizzy, From what i heard sounds like a PITA to take off the intake Plenum... Would like to AVOID at all costs lol.

[jaworski88]

I am not familiar with pathfinders, but if there no Schrader valve for checking fuel pressure, you should be able to tap in the fuel line where the fuel pressure regulator is, or at the fuel pump area underneath the car maybe? Clearly you'd need to use some special fittings to connect your pressure gauge.

[Wrierblock20]

Was able to hook up fuel pressure tester, when running fuel pressure is 32PSI, when turned off after a good 15-20min its dropped at least 10PSI, Is there a way I can isolate the fuel rail? Also should PSI be steady for hours? or fall after some time? 15-30min

[jaworski88]

Does it take longer to start after the car has been sitting for awhile for at least a day? If yes, then I'd think the fuel pump is faulty.
I have yet to check the fuel pressure on my QX4, but on my other cars, I don't recall it dropping that much after shutting off the engine for a few minutes.
So where did you hook up the fuel pressure gauge?

[Wrierblock20]

Fixed it 100% replaced number 2 cyl fuel injector, friggen purrs like a kitten and no longer smells rich. Was a leaky injector.

[Saabjock]

My wife's 03 Pathfinder is experiencing a similar issue which is pointing to either a leak at the injector itself or the seal.
She was complaining of a random 'skipping' at idle.
The initial check and code (P0301) pointed to a misfire in cylinder #1.
I did a compression check, tested the plug...then changed the coil for that cylinder and cleared the code.
It drove quite a bit better but had a longer than usual re-start after being driven and shut off for about an hour.
Yesterday I isolated the return line from the fuel pressure regulator and put a fuel pressure test adapter and gauge in line at the damper.
At key on, the pressure went to 44 PSI and then over a period of an hour fell to 10 PSI.
That to me, suggest a leak somewhere in that fuel rail...since none is leaking through the vacuum ports of either regulator or damper.

[Wrierblock20]

Mine originally was misfiring under heavy load, finally it just got so bad I changed dizzy fuel filter spark plugs and wires, the real big changed happened when I ran Royal Purple Max Injector cleaner in 10gal of gas, ran 2 tanks of the stuff this fixed my misfire under load but I had cylinder 2 misfire only upon warm restart and i5 would go away after 2-5 min of running, even some mornings I had to crank for a solid 6sec twice for the truck to fire up, but essentially only misfire after war restarts I imagined it went like this the injector leaked fuel into the cylinder while off when I would restart while still warm the cylinder was flooded with gasoline so it would misfire until the flooded gas cleared up once it did it ran fine until I shut off turn back on after sitting 10min or so and yes like you I fuel tested put the fuel gauge on delivery line then crimped behind fuel pressure gauge and return line as soon as wife turned off car the psi fell to 10psi over a 30ish min period .. lucky you it's cylinder 1 I had to take plenum off but it wasn't that bad I left coolant lines attached and just hung it up.