# 2005 Pathfinder P0300 Random cylinder misfire



## hextreme2000 (Jan 26, 2008)

Hi all,
I thank everyone in advance for any help or advice on this, it's much appreciated. 
I got my check engine light on today and it's been flashing on and off. Last night I started to notice the truck having a hard time going up hills and making a weird harsh noise coming from the engine. After I got the light on today I drove it to Autozone and they read me the code P0300 which says possible causes could be Ignition system fault fuel system fault, large vacuum leak, MAF sensor fault, Air fuel/heated oxygen sensor.
I drove it home slowly trying no to put it under hard acceleration since I can feel the engine really struggling and the shifting is not smooth at all as it normally is. I was wondering if anyone had any experience with this.
I also wanted to mention that a couple of months back I got the code P455 which I think is pretty common on Nissans, and after doing some research online I ended up replacing the valve above the evap canister and that seemed to fix the problem. I don't know if this is related at all to the evap system. Is it even worth it start changing maybe the oxygen sensor by the air intake or change spark plugs? BTW I have about 60,000 miles on it.

Thanks again http://www.NissanForums.com/images/smilies/awais.gif


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## ncpathfinder (Mar 28, 2008)

PO300 is a multi-cylinder misfire. I'd bet on the coil packs. Probably one or two of them needs replacing.


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## nissandriver2005 (Jan 31, 2011)

*Regarding P0300 CODE*

Hi,

I noticed your inquiry on the code p0300 you received a couple years ago on your Nissan and I am currently having that exact problem with my pathfinder. I wanted to ask you what it ended up being and if it was an easy fix? Thanking you in advance for any input! 




hextreme2000 said:


> Hi all,
> I thank everyone in advance for any help or advice on this, it's much appreciated.
> I got my check engine light on today and it's been flashing on and off. Last night I started to notice the truck having a hard time going up hills and making a weird harsh noise coming from the engine. After I got the light on today I drove it to Autozone and they read me the code P0300 which says possible causes could be Ignition system fault fuel system fault, large vacuum leak, MAF sensor fault, Air fuel/heated oxygen sensor.
> I drove it home slowly trying no to put it under hard acceleration since I can feel the engine really struggling and the shifting is not smooth at all as it normally is. I was wondering if anyone had any experience with this.
> ...


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## babit71 (Feb 7, 2016)

Mine starts good when cold, as soon as I drive it on the highway that's when it does the same (flashing check engine & loss of power). I changed the upstream O2 sensor, changed spark plugs but still does the same. Inputs anybody? Thanks.


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## smj999smj (Jan 1, 2006)

babit71 said:


> Mine starts good when cold, as soon as I drive it on the highway that's when it does the same (flashing check engine & loss of power). I changed the upstream O2 sensor, changed spark plugs but still does the same. Inputs anybody? Thanks.


What year Pathfinder?


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## babit71 (Feb 7, 2016)

2006. Bought it couple of months ago.


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## Indypathfinder (Jun 10, 2016)

I have a 2006 Pathfinder doing the same thing. I've changed 5 out of 6 coilpacks (PS firewall is a pain). New plugs, new O2 sensors, new cats. I still have the same issue. Did you ever resolve your problem?


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## Glamisman (Feb 12, 2016)

The P0300 is a difficult one to solve but what it IS telling you is that something is effecting all 6 cylinders. I would start with inspecting all of the external vacuum lines, the vacuum canister, the power brake vacuum lines etc. yes, it is a pain but my guess is that there are multiple small problems. My P0300 for my 99 was a combination of vacuum leaks and bad grounds... The 99 Pathfinder grounds for the ECM/PCM and the O2 sensors are on the top of the intake manifold and while they worked enough to start and run the motor the voltage drop was sufficient to "confuse" the PCM into doing things it was not supposed to do.


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## Indypathfinder (Jun 10, 2016)

Thanks.....I think you are spot on with a bad connection confusing the computer.....I am also able to wiggle the wiring harness and receive mixed ohm readings. Although a bad ground would be 'easiest'....(if it's able to be found!) there is surely something going on in the harness as well. I'll provide updates as they become available.


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## Glamisman (Feb 12, 2016)

The "bad ground" issue is not so much an ohm reading variation as it is a voltage drop situation. Nissan recommends that there be no more than a 20 milli-Volt drop on ground wires. You will need a decent digital meter that can measure milivolts DC. Put one lead one the ground in question and the other on the head/block - where the battery ground is attached while the vehicle is running and watch the meter... mine was from 420 mVolts to 700+ mVolts. It was jumping all over the place. Nissan makes a very expensive ground harness, $120. I made mine in about 10 minutes for maybe $20 in parts. I made additional ground straps for the motor to the chassis, chassis to the negative battery post, negative battery attachment on the block to the O2 sensors and ECU ground on the intake. After these additional grounds I re-ran the voltage drops and all were close to .1 mVolt. My 99 Pathfinder which I bought for $100, has been very abused and not taken care of very well but for $100 I took a chance.


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## MisterPathfinder (Jul 16, 2016)

Guys, Im having a problem detecting why my 06' Pathfinder is throwing the P0300, P0011, and P0021.
I changed my timing chains.
Replaced both camshafts sensors.
Replaced both camshaft solenoids.
Changed my Oil.
Changed all my coil packs.
Changed all my spark plugs.
Cleaned my MAF sensor.
Checked for vacuum leaks with Carb. Cleaner (nothing).
Used Dy electric on all my electrical connections.
New Battery and Alternator in the past couple years.
And my electrical harness' appear to be in good shape. 
Also, I have bad Cats. Exhaust smells like eggs.

*Need some info or advice fast!


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## smj999smj (Jan 1, 2006)

If these occurred after the timing chain replacement, it could be that the timing chains where not installed properly and the mechanical timing is off.


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## Peterdz (Apr 1, 2021)

I read on another forum that the fuel rail on the side of 1,3 and 5 cylinders is typical for clogging up. I have a 2005 Pathfinder and I'm getting the same multiple misfire code and have changed several coils, the air flow sensor, spark plugs, have done the carb cleaner test on the intake with no luck. I'm going to clean the fuel rail this weekend and hope that will fix it.


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## smj999smj (Jan 1, 2006)

Peterdz said:


> I read on another forum that the fuel rail on the side of 1,3 and 5 cylinders is typical for clogging up. I have a 2005 Pathfinder and I'm getting the same multiple misfire code and have changed several coils, the air flow sensor, spark plugs, have done the carb cleaner test on the intake with no luck. I'm going to clean the fuel rail this weekend and hope that will fix it.


I'm an Admin @ TheNissanPath.com, where we see a lot of R51 traffic in our posts, and have never heard of any issues with fuel rails clogging, so, let us know how it goes.


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## Andy30 (Jun 29, 2021)

hextreme2000 said:


> Perhaps Nissan made some reasonable cars before, but as of the latest they have been a very disappointing company.
> 
> Even the engine on my Nissan is, sincerely speaking, a long way from most common expectations. Very noisy, both when driving and in idle. As soon as it is a bit warmer outside, one could hear the dowels as if the engine would burst from one second to the other. Pray to God that nothing happens when being on the highway. I feel it has only been a matter of luck so far that I did not end up stranded in the dessert.
> 
> ...


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## VStar650CL (Nov 12, 2020)

smj999smj said:


> I'm an Admin @ TheNissanPath.com, where we see a lot of R51 traffic in our posts, and have never heard of any issues with fuel rails clogging, so, let us know how it goes.


+1. I've never seen a clogged rail on a Pathy either, old or new. More likely it's bad fuel, bad engine grounds, a hidden vacuum leak, or a spotty cam or crank sensor. If they're all on the same bank you can add the A/F (front O2) sensor to the list.


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## C_Marie92 (Aug 29, 2021)

Hi! 
I'm looking for some input here, for an 06 Pathfinder. I'm getting p0300 code reading. 
I had the coil packs changes as well as the plugs but my vehicle is still acting up. 

Issue started abruptly while I was out running errands, I noticed it was taking a bit to accelerate. Got it home asap, next morning it drove fine breifly, then just wouldn't go over 40 mph. From 40 dropped to not going over 20mps now.

I don't know much about vehicles so any help here would be greatly appreciated.


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## smj999smj (Jan 1, 2006)

C_Marie92 said:


> Hi!
> I'm looking for some input here, for an 06 Pathfinder. I'm getting p0300 code reading.
> I had the coil packs changes as well as the plugs but my vehicle is still acting up.
> 
> ...


I replied to your other post: 06 Pathfinder/Loss of power/ won't accelerate over...


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