98 Pathfinder Multi Misfires P0300

[Wrierblock20]

Two codes P0300 Multiple Misfire & P0325 Knock Sensor circut Bank 1. Heres whats going on when starting the vehicle takes a little while longer than normal at least 3-4 seconds of cranking and its choppy when lt starts but always starts, it's rained here the last few days but it's finally cleared up, after driving when dry the pathy has developed the check engine light after its warmed up the light will flash a bunch of times when this happens it barely accelerates and is so jumpy and barely wants to go I have not had it stall though even at idle the truck will feel like its jumping around just misfiring like crazy it seems, I can still accelerate just really poorly, if I push on the gas heavy it still can go fine but gradually it has a problem, randomly after CEL flashes then goes solid the truck will just start running perfectly fine as if nothing's wrong but after a bit will misfire again and keeps happening, I bought this truck at 190,000 now has just above 200,000 I have no idea what maintenance has been done in its life time.... What should I begin to look at for troubleshooting? This is my only vehicle please I love my pathy, help! So far I have cleaned MAF sensor, changed oil since issue happened, ran tank of fuel system cleaner with high octane gas, checked cap and rotor all seems good there. Trucks got 205,000 bought at 190,000 also changed air filter, also to note I pulled of air flow tube going to throttlebody where the butterfly throttle connector is and I did spray some cleaner in there and notice its pretty black nasty in there was dribbling out black s*** I cleaned it up the best I could though.

[04pathse]

did you check the spark plugs?

[jaworski88]

I am kind of going through the same with my newly acquired QX4, except that I bought mine with that known problem. Check the Service Manual available on this forum, it may have a procedure for diagnosing the misfires on your vehicle. The manual for my QX4 does, and it walks you through the steps of checking the spark plugs, injectors (voltage, clogging), ignition coils, fuel pressure, etc.
I'll let you know soon as I figure mine out...

[Wrierblock20]

I just ordered ngk plugs / ngk wires / fuel filter / distributor, wont be able to start the part changes until Sunday when they arrive but will also let you know.

[jaworski88]

You could try a more powerful injector cleaner. Can you hear injectors clicking? You can check if voltage is getting to your injectors, and i'd check the fuel pressure as well.

[Wrierblock20]

I used a Mechanics Stethascope and each injector sounded flush and firing good even when misfiring. Have not tested the voltage yet though, I mean maybe one injector failing but mutli of them at once and ontop of that it having the issue intermittently then acting fine again then having the issue again is just weird, Possibly fuel pressure like you said, I'll have to rent a tester for that if these new parts don't resolve, I have my money on the dizzy but we shall see, (Hope Im right) LOL...

[jaworski88]

On my QX4, there is something called an ignition condenser coil, that could also be the cause of misfires. It's like a $7 part from the dealer. Research on whether or not your Pathfinder has one. Worth a try...

[Wrierblock20]

I have the model that has a distributor my Ignition coil is built into the Dizzy , So gotta replace the whole thing! It's not a part I can just pull and replace. 2001+ Has Coil packs like yours. And to top it off my parts were delayed until Wed

[jaworski88]

Update: I think I got a little lucky. The sales guy at the Infiniti dealership gave me a good discount on parts. So this weekend I replaced the ignition condenser coil (old one had gooey stuff on it), replaced the ignition coil and spark plugs. That fixed the misfires, but now I think the misfiring damaged my catalytic converter because it is kinda loud now. Has anyone heard of that, misfiring damaging a catalytic converter? It almost sounds like a motorcycle now, and it's clearly coming from the converter. I am just glad that it doesn't misfire anymore and the CEL went off on its own.

I'm thinking that the PO replaced the coil with a bad one (non-genuine brand). It had a much higher resistance than the new I got. Hope this helps someone...

[Wrierblock20]

Awesome glad you were able to get that issue fixed, As for the CAT yes Misfires can burn up the Cat, Basically when the vehicle misfires it leaves unburnt gasoline which then gets allover the CAT and then can catch fire inside the CAT overheating it basically destroying it, if theres a rattle then sounds like parts inside the cat for filtering have broken loose and are rattling around in there, or maybe its plugged.