2006 M35 Injector #4 R&R advice needed

[steve_c]

Hey all,
Still chasing down a code PO304 #4 cyl. misfire, 2006 M35x, 115k miles on original plugs.
I changed out plugs & all coils. Code PO304 still present, no other codes.

I am going to change injector #4. Any advise on best way to do this with minimal disruption to the fuel rail & other injectors?
I am taking the plenum off completely. Are the metal injector to rail clips re-usable? Are they difficult to remove without mangling them? Any tips/tricks on keeping most injectors in place while getting at the one needing to be serviced?
Thanks

[EdBwoy]

As much as the code is still there, is the car acting any different? Just asking because in my experience, Nissan codes stay around a little even after the problem has been fixed.

I would still move the coil around just to see if the code follows... But you seem to have a good understanding of what you're doing and have probably isolated the problem to an injector issue. Since you're definitely removing your injector: I don't know of any shortcuts to injector removal in the M35 V6, but yes those clips are reusable in all the fuel rails I have done. WD-40 or engine oil would be your friends to lube up the rubber o-rings.

Unfortunately, since #4 is in the middle of the rail, you kind of have to lift the entire rail on that bank. (Please don't bend the rail, or things won't seal just right upon installation).

So, WD-40 on all the o-rings at the point they enter the head/intake.
-Wiggle the rail back and forth gently
-In as smooth a motion as you can manage, pull the rail up.
-It's way easier to mess with the clips after the rail is off.
-One thing to watch out for is the fuel injector pintle caps. They are prone to popping off and falling back into the injector ports. Pretty sturdy, but they could break as well. Did I mention WD-40? The lube helps the o-rings slide out easily so that they don't push the pintle caps out. If you're careful with it, all components will be reusable.

Again, this is just my generic advice from tearing Nissan engines apart. Good luck!

[steve_c]

Thanks EdBwoy,
I did swap out coils, made no difference, stayed with #4. At that point I went & changed out all 6 coils with new ones, same code, no movement. The engine definitely has a miss, and it is staying put, not moving around. I knew as I was testing coils & installing plugs that problem was still there even before the code re-appeared after clearing. The miss is at #4, with coil connector disconnected & engine running, engine miss remains even after reconnecting coil. Before installing new coil & spark plug at #4, I connected the assembly & ran the engine. Spark is present! Every time I road test after I do anything, I get a cat overheat warning once the car gets to engine op temps, so I know the issue still persist.

Back to the fuel rail, I am going to remove all rail hold down bolts, & gently lift up the left (drivers side rail only) leaving the other side alone, that is, leave right side injectors attached. From your reply, sounds like I leave the injectors attached to the rail side & lift them out from the bottom (engine), plenty of WD as noted. Does that sound right?

[EdBwoy]

So, the injector might be stuck open... or somehow operating erratically enough to dump fuel, huh?

Yep, you got it! There are usually 2 rail hold down bolts per bank. Careful not to lose those black fuel rail dampers as you lift the rails too.
Also IIRC the fuel rails for the 2 banks in the vq35 are continuous, in that its one bent tube, while the vk v8s have some flex hose in between. You might need to lift the entire rail if that's the case in yours.

[steve_c]

Update

I separated the top half of the plenum & gently pulled it up & back leaving the throttle body on it, as well as the water line going to it. I had plenty of room to remove the lower plenum, which I did. What a shocker:

The #4 injector harness plug wire is shredded off from the connector right at the base. The wiring insulation, as well as the conduit around it is shredded as well. It does not appear to be shorted to anything, so hopefully the PCM is OK. Almost seems like a small animal chewed at it.

The #1 injector harness has worn through in one spot exposing the wires within. That seems like a rubbing issue between the harness & the roof of the lower plenum. Fortunately, the wiring insulation has not chafed through, and that injector is firing OK!

I know there are Injector connector pigtails out there. If anyone knows where I can get a few of them that will fit,I would appreciate it!

[steve_c]

Found injector connector pigtails.....won't arrive until Nov. 20th., shipping from CA (to NY)!

[EdBwoy]

What is it about wires that attracts animals like mice to them? I would be tempted to set up bait in the valleys of my V engines, but I'm not thrilled about dealing with smelly, dead animals.

Anyway, glad you located the issue. Post up a picture of your existing harness and connectors, or PM me so I see what I can do for you. I think I still have my vq35 harness from an i35


EDIT. Nvm, just saw your update. It's just a few days out. Good luck

[steve_c]

Thanks EdBwoy.....
The pigtails shipped out, might be lucky to get them by Wednesday!
I will post a photo of harness. Still a few questions I have, the coolant line under the throttle body. Does the coolant flow through the throttle body or does it flow through the neck of the plenum (near the throttle body), or through both?
Can I leave the coolant lines attached & just remove the 4 bolts securing the upper plenum to the TB?
If I remove the TB from the plenum, am I at risk of having to re-set or re-map the PCM afterwards? I do not see why I would have to providing I do not clean the TB or plenum.....

[steve_c]

Code PO304 #4 cyl misfire Repaired!
Sorry I cannot post the pic I took of the findings, (no photobucket). Long story short, my #4 cyl. misfire was due to a broken (chewed off) wire at the #4 cyl injector harness connector! It was positively caused by some small rodent. I found a generic connector pigtail set on E-Bay. Though slightly different from the OEM connector, It fit snugly onto the injector, the pins line up,the tab locks securely, and there are weather seals both inside & out. The new pigtail ohmed out nicely, so I soldered it into the harness & put it all back together. While replacing my original spark plugs (115k miles on them) I installed 6 new Hitachi coils. I only put 10 miles on the car since the repair, but so far so good! My only leftover part was the new fuel injector I bought and did not install. Cost me $60.00+, but just chump change compared to what I would have paid to have the problem diagnosed & serviced at a shop!
Shout out to EdBwoy for his assistance with fuel rail & injector service advice, happy I did not have go that route this time around!

[EdBwoy]

Good job SteveC, and glad you got it back on the road without too much trouble! Might as well sell that injector if you can. I don't think newer Nissans have many injector issues
If you're open to sending me the pictures you took, I can post them here for you.

And sorry I didn't catch your question on coolant earlier. For cars with lines to the TB, I believe the coolant is meant to pass through the throttle body to prevent air moisture from freezing. There is a mod where people in warmer climates bypass the throttle body.
I don't usually modify mine because:
1. Cars get sold. A bypassed car in Florida today might end up giving a new owner headaches in Michigan next year.
2. Well, I live in a cold climate. Haha

And I bet you've figured this out, but just unbolting and reinstalling the TB shouldn't cause any issues.

[Ilya]

Love this place. Good work guys.

I also don't recommend the TB bypass, but I live in NY which gets just as cold if not colder than Iowa. Listen to EdBoy .

[steve_c]

EdBwoy,
I would love to get one photo of the damage posted. How can I get the jpg image to you?

Since you & IlyaKol mentioned the TB coolant bypass issue & its drawbacks, I see there is a 5/16 plenum spacer modification kit available. What do you guys think of this?

[EdBwoy]

Ilya, Nicoclub is a truly nice place to be. As much as I try to contribute here, you have no idea how much more I have gained from here.

Steve, email it to [REDACTED] and I'll make it happen.
As for the spacers, one thing it does is to detach the throttle body from the intake manifold. I have seen them marketed for 2 things:
1. To keep the throttle body cool(er), which is contrary to what the antifreeze lines purport to do.
2. Airflow dynamics for incoming air.
Both of these are supposed to improve performance. I didn't buy it (pun intended), but I believe a good number of g35, 350z and maxima owners have them. No personal experience though.

[Ilya]

I had the 5/16" Copper ISO Thermal IM spacer and TB spacer on my 2007 (whoever bought that car got lucky ). I didn't disconnect the coolant lines, just moved the TB a bit to add the spacer. I highly recommend that product however you'll likely need an UpRev tune to get it's full benefit.

Steve, please update your profile to show your general location.

[EdBwoy]

EdBwoy,
I would love to get one photo of the damage posted. How can I get the jpg image to you?
...

This was the cause of Steve_C's P0304 code

[Ilya]

Yep, that'll do it lol.