05 Pathfinder issues please advise code P0174 lean bank 2

[curvecrazy]

I'm kind of frazzled here. 05 Pathfinder has check engine light with 96K miles. Been on for a few weeks now. I've been fooling around trying to sort it without success. Had local auto parts store scan it when I first got the light to see what the hell.... PO174 Lean condition bank 2 which is the drivers side on the 4.0 V6 engine. Cylinders 2, 4 ,6 respectively.

I've got limited knowledge here. I do have the service manual on CD and have spent hours reading that to better understand this scenario and hours on the internet too regarding others experiences here which didn't really get me anywhere frankly. One poster claiming be a ase cert. mechanic saying it is definitely not an O2 sensor so don't waste your money replacing that..... Which was kind of disheartening cause I had hoped it was that. fwiw

Based on my research, what I've found is that it can be:

- Intake manifold air leak
- Exhaust manifold air leak ahead of / before the O2 sensors catalytic converters
- Low fuel pressure
- Faulty fuel injector/s
- Possibly MAF sensor (but seems it should then put out lean codes for both banks 1 and 2 no?)
- Possibly O2 sensor before or after catalytic converters ( 4 cats on vehicle and 4 O2 sensors the rears both heated)
- Incorrect PCV hose connection

I have worked on this awhile. Started after the check light and code reading with a Lucas fuel system treatment. Crossed fingers and hoped. Light went off, car ran better shortly, then light back on and car started to hesitate/sluggish on freeway driving home. Seemed sort of like bucking behavior.

I assumed the computer was richening the mixture on bank 2 and that the plugs were fouling out as such as maybe there was an air leak or bad injector on one cylinder but the computer just hits the whole bank with the richer mixture adjustment. ??? Or was my understanding it can't just richen one cylinder. So I removed battery negative to clear the code and get baseline setting in hopes of burning off the fouling on the bank 2 plugs. Car seemed to run alright afterwards on way back to work. Light came on again after 25 miles. I repeat to go home. And same. Repeat to come back. Did it several times to avoid the sluggishness and what seemed to me to be fouling behavior. Drove it gently in the interim.

As soon as I had time to work on it I did. I could not detect any vacuum leaks by ear or sight. Engine fan runs all the time off the front serpentine belt and its too loud and too much airflow over the engine compartment to figure out anything. I tried starter fluid on fittings. I tried propane at fittings. No obvious change in engine idle but its so damn loud in there who knows? LOL I have no smoke machine. So I removed the MAF in the intake and fashioned up a plug for the intake with an air compressor fitting. I pressurized the system( I know.. careful not too much) to probably 3psi or so. Enough so there was pressure and applied soapy water solution via spraybottle and reservoir/brush too depending fitting. Gave all a good dousing. No bubbles and no signs of leakage. I know there was pressure cause when I remove my air line the pressure comes forcing back out the fitting. It also seems me the PCV would not allow pressure past it but that system has an intake to the valve covers and a cross tube to allow fresh air in to so maybe I did have that pressurized too. I should have removed a tube to see but did not think of it at the time. I may have missed the fitting in the back the engine compartment for the brake booster. Its by the PCV and out of sight... Which I can check.. just noticed it last night when fooling with removing the PCV. I pulled the pcv valve and it was somewhat crudded. I cleaned it out with degreaser the best I could do. I know the spring operates freely and at idle there is strong vacuum through it. Block it off and the idle changes slightly. fwiw As was specified in CD manual.

After I pressurized my intake system. Found no leaks. I carefully cleaned the MAF with ISOPROP. Alcohol and a artists detail brush... very gently and carefully. I also removed the air filter housing and washed it down crystal clean in the kitchen sink. All dust residue gone. Also wiped out the intake best I could at the MAF and further too. Some said that might fix the problem. Put it back together and drove to work the next day. No light. Back home no light too.. ! Hmmm me thinks. The light did come back on though after awhile maybe three trips or 65-75 miles. Back to parts store. Same code again I find. PO174. I was hoping a different code fwiw. Anyways. I can't see any sign of an exhaust manifold leak although both areas are tight spaced and covered with heat shields which make assessing quite difficult really. I listen to both with long rubber tube inside the heat shields and back to my ear and its pretty noisy the same it seems on both sides. A lot of clattery noise probably the valves working or whatnot? I had an exhaust leak just before the muffler which is behind the cats and O2 sensors too. I fixed it to an extent. Probably 75% closed off with metal can sheet and clamps. fwiw. Overall vehicle noise level dropped off a lot by doing that and I did that before attempting to listen to the exhaust manifolds so I could best hear.

So.. Question is do you have any ideas? If not, could you recommend a course of action here? I am afraid of damaging the catalytics by driving it further while I continue to funck around with it. The dealer want's $100 to look at it and tell me the problem - if possible - in one hour. If not then $100 each consecutive hour. I am not familiar with this emissions code stuff and compliance much and honestly had hoped never to get familiar with it.. [emissions code faults and NYS hand in hand and the nightmares I perceived it to be No Shit.... ]. Can't inspect with CELight on and exhaust emmisions goes straight to albany via computer no amount of trickery getting around it I am told fwiw. So here I am in the thick of it. I don't need an inspection for months but I don't want to damage the engine driving it but I do have to get to work 25miles and there's no riding the bike in the snow we have here.......

I have been told by various that they had the code[ this one exactly or others] and spent much money at the dealers who replaced various parts at great expense and did not cure the problem or the light came back..... This being the PO171/PO174 codes which would be lean bank codes. Am I better off to do the dealer route with this? Assuming they have expertise??? Or can a mechanics shop manage this problem better? Are the tools available to them the same in terms of the code readers and diagnostics or Nissans more better/specific?

Can I buy a code reader for reasonable and if so which would you recommend? Attempting this without one has been a hassle and I assume some are more better/specific than others? Getting a reader that would give me a MAF code say vs one that says just "lean bank 2" would be helpful. LOL Is that just a dream?

Right now I am close to pulling the intake off the top the engine and inspecting fully for cracks. This would get me to the throttle body just underneath and the fuel injectors and I could probably remove the throttle body, spin the motor and watch the "patterns for evenness. The only thing I know to do to physically check the injectors for proper spray if you will.... I was wondering if I could have dissolved something in the fuel filter/system and caused it through the fuel injectors... But then again, it would have to be smaller than the fuel filter media itself and wouldn't that then pass the injector passages? You see I have issues!!!! But, the light was on previously to that engine treatment being applied.. Its just the sluggishness started after that... at first after the fuel treatment the car ran great and the CEL went away... then the light came back and I had the sluggishness on the way home. So that led me think maybe I caused a problem with the Lucas stuff. Which now I think about it probably not. I hesitate to remove the intake and the injectors due to the top the engine being very dirty and sand and shit being in the injector holes above the seals. I'm afraid as careful as I may be I would get some in the intakes which............... I tried to clean it but its dastardly and shit in the crevices everywhere fwiw.

I don't have a fuel pressure gage to access fuel pressure unfortunately but I could buy one. Think?

So really.... I know, I know, Give me a break right? Why me he has to hit with this shit right? I am sorry Rob. I know you have experience with this and I just thought you might have some relevant advice here to save me excess trouble. I could use some good advice from someone who knows... The question is, do the dealer mechanics know.. or will it likely be a situation like you described where they could not figure it out and give the shit to you to fix and etc... as per your emails last year mentioned.......

Another just told me about the IPDM faiure he had that gave the same PO174 code and nissan is offering free replacement of the ECM relay on 05-06 pathfinders and maybe frontiers/Xterra's too . May even be my problem too. Shows apparently as idle stumble or dying at idle. Bad contacts. Go to your dealer.

Hmmm. Please help me here. LOST somewhat. Hope you're having fun in the sun +++. George