P0174 trouble

[Xandor360]

So I just picked up this 2001 pathfinder and as expected not to long after I got it check engine light came on.    P0174 is the code that is coming up.  Also it will not idle when cold and has an extremely rough idle when it has warmed up a bit.   I have changed the air filter and MAF.     Also checked for vacuum leaks in the most common places.   Will need to smoke test it at some point.    I bought this a future build as well as a mountings/hunting rig.   Need this engine to get me through to winter.     Any help will def be appreciated.    

[Xandor360]

Well, here is an update.   Turnes out I had 2 problems with it.    Small vacuum leak in the intake manifold as well as a bad connection to the MAF.   Smoke testing the intake was a huge help.   I would have never found that otherwise.   3$ junkyard connector and problem solved.   Now here is the next question.   How long do you think I can get out of that engine?   It has 300K on it and I'll be happy if I get 10k out it before I have to do a swap or a rebuild.    While I had the manifold off, I went ahead and changed the plugs, new vacuum lines, coolant lines behind the engine as well as valve cover gaskets.    PCV valve as well.   Anything else I should take care of while I have the intake off?    Also, I am wondering what type of tires people prefer for their stock R50 as well as size?    I do not mind if I have to trim anything.     

[Slartibartfast]

Good work! Those smoke machines are nice.

 

At 300k, I think longevity is going to depend more on how well the last owners looked after it than anything else. I would loctite the power valve screws while it's open, they have a reputation for working loose and falling in. Keep an eye on the oil level once it's back together! Some of the VQs are oil burners.

 

The cable-throttle VQ R50s also have an idle air valve that can leak coolant into itself and blow up the computer. I don't remember if it's just the gasket or the valve itself that goes bad. Something to look into.

[Xandor360]

Good to know about the power valve screws.   I have already ordered a new valve and gasket for it.   When I was removing the TB it looked corroded so figured it could not hurt.   Next question is when this engine goes where to source a low mileage engine and tranny or should I just rebuild the one I have.   I have also thought of getting a junkyard block and just doing the build myself.   Any thoughts?  

[Slartibartfast]

That's a good question. A used engine/trans would be easier (and probably cheaper as well!), but might have its own issues--like I mentioned, some of the early VQs had oil consumption issues. (I've heard various theories about what actually goes wrong--PCV design, cylinder taper, catalytic converter bits getting sucked back--but I don't remember reading about someone with the oil consumption actually fixing it. My dad's '03 burned a quart/1k miles before 100k, and it acted like the valve stem seals were bad, but we never tore it down to see what was wrong with it.) Rebuilding yours (or a donor engine) may get you a better product, assuming you don't mind the added cost and time, and of course assuming you have the skills to pull it off.

 

Also consider compatibility. Nissan changed a few things across the four years the VQ was used in the R50. '01 and '02 were both cable-throttle ('03-'04 were drive-by-wire), but IIRC the '01 had different valve covers and coil packs? I would expect '03/'04 engine to work if you used your old intake, but I don't know that. Do some research on this to make sure you get the right stuff.

 

It'd be great if a more modern VQ (with the early bugs ironed out?) would work, but that sounds like a science project waiting to happen--who knows what else they've changed in the last twenty years.

 

Unless you've got the five-speed (rare with the VQ, but they do exist), I think all the VQ R50s got the same four-speed auto. That one should be simpler to track down.

[CamperDan]

7 hours ago, Slartibartfast said:

That's a good question. A used engine/trans would be easier (and probably cheaper as well!), but might have its own issues--like I mentioned, some of the early VQs had oil consumption issues. (I've heard various theories about what actually goes wrong--PCV design, cylinder taper, catalytic converter bits getting sucked back--but I don't remember reading about someone with the oil consumption actually fixing it. My dad's '03 burned a quart/1k miles before 100k, and it acted like the valve stem seals were bad, but we never tore it down to see what was wrong with it.) Rebuilding yours (or a donor engine) may get you a better product, assuming you don't mind the added cost and time, and of course assuming you have the skills to pull it off.

 

Also consider compatibility. Nissan changed a few things across the four years the VQ was used in the R50. '01 and '02 were both cable-throttle ('03-'04 were drive-by-wire), but IIRC the '01 had different valve covers and coil packs? I would expect '03/'04 engine to work if you used your old intake, but I don't know that. Do some research on this to make sure you get the right stuff.

 

It'd be great if a more modern VQ (with the early bugs ironed out?) would work, but that sounds like a science project waiting to happen--who knows what else they've changed in the last twenty years.

 

Unless you've got the five-speed (rare with the VQ, but they do exist), I think all the VQ R50s got the same four-speed auto. That one should be simpler to track down.

He's gonna want to stick to the VQ35DE that came in R50s 2001-2002 only, because the VQ that's in the 2003-2004 R50s has a few other changes beside from the drive by wire throttle body. I was also was planning on sourcing a spare engine from the junkyard out of an 2003-2004 R50, but according to our late friend @Dbot there's other things that have been changed like the cam phasers, sensors etc, so it won't mesh with his R50s current computer. He advised me of this as he was thinking about doing the same in the past, but after doing some research he came across some of these differences in the engines.

 

Chris.

Edited June 29, 2024 by CamperDan

[Xandor360]

Yeah I have been looking for engines online a few places.    I found a pathfinder R50 2000 on copart that I am thinking about picking up.   None running but it is a 4X4 and if im lucky it might have a limited slip in the rear.    Who knows what I will do with this one.   I will be honest though I am quite happy with it so far.   Next weekend comes servicing front and rear axles, transfer case and whatever else I can lube up under there.     

[Slartibartfast]

Nissan was still running the VG33 in 2000, so if you're looking for an engine, that's not a match.

 

The R50 LSDs were nerfed hard from what they were in the WD21. Hawairish has an excellent writeup for repacking the R50 LSD to be worth a damn. The early (first couple years IIRC) Xterra LSD is supposed to be a drop-in upgrade if you don't want to tear the diff all apart, but you do need to check the gear ratio and make sure it matches the front end.

 

@Camperdan, thanks for the correction! Shows what I know about the VQ35.

[CamperDan]

On 6/30/2024 at 6:55 PM, Slartibartfast said:

Nissan was still running the VG33 in 2000, so if you're looking for an engine, that's not a match.

 

The R50 LSDs were nerfed hard from what they were in the WD21. Hawairish has an excellent writeup for repacking the R50 LSD to be worth a damn. The early (first couple years IIRC) Xterra LSD is supposed to be a drop-in upgrade if you don't want to tear the diff all apart, but you do need to check the gear ratio and make sure it matches the front end.

 

@Camperdan, thanks for the correction! Shows what I know about the VQ35.

Hey like I said I was corrected on this topic once in the past too, and I'm still learning. That's what makes this site such a great place for all R50 Owners, I don't know everything but NPORA does. I have spent countless hours in the past doing research and asking questions here on NPORA, and just learning to leverage other like minded R50 enthusiast.

 

Chris.

Edited July 4, 2024 by CamperDan

[Xandor360]

That is definitely good information to know.    Thank you.    Might have to look for a different doner R50.    I did see that video you were talking about and it is a good idea.    Any thought on using a different rear end with a LSD in it already.   I have looked at air lockers and am having a hard time spending that much.   Might just have to take it out and get it stuck a few times to change my thinking.   

[Slartibartfast]

AFAIK the R50 is the only vehicle with the 33-spline H233B and rear coil springs sold in the US, so your only whole-axle donor is going to be another R50. I don't know that swapping the whole axle would be any less work than swapping the early Xterra 3rd member into your existing axle (assuming you can find one). If you do go looking for a whole R50 axle, avoid '03/'04--they got nerfed down to less breakaway torque than the lug nuts take.

 

Make sure any rear axle or 3rd member you pick up has the same gear ratio as your front diff. There's a plate in the engine bay with the VIN and other info. You want the number that starts with HG. Should be HG43 or HG46.

 

I'm happy with the LSD in mine. It's not a locker, and it never will be, but it's a big upgrade over an open diff. And mine was made before Nissan started nerfing their LSDs, so I didn't have to open it up and fix it! It does get a little tail-happy in the snow, though, which is probably why the later LSDs were nerfed.

[Xandor360]

Yeah I took a look at all this over the past few days and have been looking into some things as far as front and rear axles go.    I am currently running the HG43 rear end with gearing in the front to match of course.     I did watch that video for super packing the LSD which is interesting.    Might have to give that a try here in that future.    Right now the gearing is fine for what I am planning on doing.