Misfire and Hard Start Troubles [SOLVED - fuel pressure damper]

[jscricca]

Quick recap of my 03 Pathfinder LE. We bought it about 10 months ago with 90k on it. Since then I've done a few oil changes and recently replaced spark plugs (OEM NGK properly gapped) and valve cover gaskets. The gaskets were toast and leaking quite a bit of oil in the plug holes. The car has run great after that about 5k ago.

On a side note this engine is thirsty for oil. I burn and add back about 2-3qts of oil every 6k. I use Mobil 1 High Mileage. I'm convinced this is poor piston rings since there are no leaks.

Now to my current problem....

Prior to all this major work we noticed some hard starts after a month or two of ownership. Occasionally it would take a few extra cranks to start. It slowly got worse and more common. Recently it has gotten a lot worse and we started getting a misfire on idle. Some starts it takes 3-5 second to start the engine. Once you give it any gas the misfire goes away and it runs well.

I've pulled P0301 twice now (cleared and it came back). I checked cyl one, tried a new coil and plug; nothing changed. Still getting random misfires upon idle. All is well once you give it gas and are driving.

My gut tells me this is a dirty or failing injector on cyl. I've been hesitant to diagnose more on my own or take it into the shop because I know getting the intake manifold off is a PITA (2-3 hours based on my last experience).

I just put a whole bottle of Techron in a full tank but the problem still persists, perhaps its slightly better. Next I'm going to try a bottle of good old Seafoam.


What are your thoughts? Do you agree this is likely an injector or could it be something else? What do you recommend for fuel injector cleaners?


Thanks!

[Upgrayedd]

Have you checked the fuel injection pressure regulator and fuel injection pressure damper? I was having a hard start issue on my '02 Pathfinder and it ended up being both. Either of those will cause a hard start issue. After you get it started let it run for a few minutes then shut it off. Pull the vacuum lines off of each and if there is fuel in the line then that part is shot. Both of mine had fuel in them when I checked so I replaced them and it fires right up now.

Both parts are fairly cheap and easy to replace. Be careful as the screws for the pressure regulator are very soft, I had to use Visegrips to remove mine.

Here's a link showing how to replace the regulator. The damper is the other similar looking part.

http://perfektadrenalin.blogspot.com/20 ... lator.html

[04pathse]

Maybe try swapping cylinder 1 fuel injector with a fuel injector from a different cylinder and see if the code follows.

Your oil consumption might be caused by the power valve screws backing out into the internals, this is a common issue with these motors and there are several threads on this forum pertaining to the issue.

search.php?keywords=power+valve+screw&t ... mit=Search

[jscricca]

Have you checked the fuel injection pressure regulator and fuel injection pressure damper? I was having a hard start issue on my '02 Pathfinder and it ended up being both. Either of those will cause a hard start issue. After you get it started let it run for a few minutes then shut it off. Pull the vacuum lines off of each and if there is fuel in the line then that part is shot. Both of mine had fuel in them when I checked so I replaced them and it fires right up now.

Both parts are fairly cheap and easy to replace. Be careful as the screws for the pressure regulator are very soft, I had to use Visegrips to remove mine.

Here's a link showing how to replace the regulator. The damper is the other similar looking part.

http://perfektadrenalin.blogspot.com/20 ... lator.html

Thanks for the advice. This could certainly be it.

That post was helpful. Why are there two FPR or is one considered a damper? The guide was only for the lower FPR.

Did you replace both? I'm trying to figure out how I can identify the culprit or culprit(s).

[Upgrayedd]

Have you checked the fuel injection pressure regulator and fuel injection pressure damper? I was having a hard start issue on my '02 Pathfinder and it ended up being both. Either of those will cause a hard start issue. After you get it started let it run for a few minutes then shut it off. Pull the vacuum lines off of each and if there is fuel in the line then that part is shot. Both of mine had fuel in them when I checked so I replaced them and it fires right up now.

Both parts are fairly cheap and easy to replace. Be careful as the screws for the pressure regulator are very soft, I had to use Visegrips to remove mine.

Here's a link showing how to replace the regulator. The damper is the other similar looking part.

http://perfektadrenalin.blogspot.com/20 ... lator.html

Thanks for the advice. This could certainly be it.

That post was helpful. Why are there two FPR or is one considered a damper? The guide was only for the lower FPR.

Did you replace both? I'm trying to figure out how I can identify the culprit or culprit(s).

That guide only shows how to replace the regulator. However, in the pics you can see what looks like another regulator but is actually the damper. If you go to rockauto.com and look up your vehicle then under "fuel & air" both parts are listed and have pics of what each looks like. The damper has a hose permanently attached to it, the regulator has a hose & clamp that pulls off. The procedure to replace the damper is very similar but you will need a 3/4" wrench and another metric wrench (I forgot the size) to disconnect the end of the hose.

Both each have a rubber vacuum line going to it that just slips on and both are checked the same way. Carefully pull the vacuum line off of each and see if any fuel wetness is inside. They should be dry. If any fuel is in either vacuum line then the regulator and/or damper need to be replaced. When I first checked mine they were dry but the vehicle had been sitting overnight. After I fired it up, let it run for a few minutes, then shut it off, I checked both lines and they were both wet. I guess the fuel had evaporated after sitting all night which is why they were initially dry.

I replaced both parts since the vacuum lines on each were wet with fuel. After repalcing them it started up perfectly without any hesitation so those indeed were the cause of the hard start issue.

Here's another link that caused me to check them:
http://x.nissanhelp.com/forums/pathfind ... rwise.html

[jscricca]

Upgrayedd is my hero. Thanks again!

It turned out to be the fuel pressure damper. I was going to replace both the damper and regulator, about $130 for both, but was unable to get one screw off regulator. I soaked this thing for two hours with PB blaster with no avail. Luckily it didn't seem to be broken.

If anyone has to do this job, I'd highly suggest PB blaster and some patience. I'd also suggest a backup plan for the screws holding in the FPR as they will likely strip.

[Upgrayedd]

Awesome, I love it when a plan comes together!

I have a smaller pair of Visegrips with a long jaw kinda like needle nose pliers that I used to remove the screws on my FPR. I even used PB Blaster on them but they were stuck. I put some anti-seize on the screws when I reinstalled them.