Nissan/Infiniti P0171 & P0174

[Hall]

The SES light came on on me yesterday and when I scanned the codes, I get P0171 and P0174. Most diagnoses say to look at the MAF (or clean it) or look for leaks in the intake. This engine, a VQ35HR, has dual intakes, two MAFs, etc so the odds of both MAFs failing or being dirty or an air intake leak are pretty much slim to zero. It does have short ram intakes on it but I clean the filters and MAFs about once a year.

I'll check the intakes and MAFs out but after this, what else should I look at ?

 

[Graham Piccinini]

 

[GSCJR]

Check for a vacuum leak.

 

[Trav]

I just did injectors for a Toyota that had lean codes last week for my friend FalconLS. He smoke tested it, checked out everything, fuel pressure, MAF, etc all good.
The injectors were flowing 50% of what they should.

 

[WeyounDS9]

when you say you have a "short ram intake" do you also have a oiled filter K&N style?
Those are poison for a Nissan/Infiniti MAF

 

[Hall]

when you say you have a "short ram intake" do you also have a oiled filter K&N style?
Those are poison for a Nissan/Infiniti MAF

They are not "oiled" filters, they're the "dry" type.

FSM

Thanks for that ! I actually have the FSM but didn't think to look in it (wouldn't have known where to start either). I'll probably print it out 'cause depending on what's wrong, it will be above my skill level. I have a good relationship with a local shop so the tech may or may not appreciate having that information. Would anyone give this to the tech that will be working on it ?

 

[JTK]

I know in the case of the VQ35DD in our 2019 Pathfinder, unbeknownst to me, I had an ill fitting aftermarket air filter that eventually lead to a MAF code. The air filter would sag in the housing when you clipped it back together, allowing unfiltered air to pass.

I tried to run it temporarily with the MAF unplugged. It started running poorly and eventually stalled and would not even restart. A proper fitting air filter and new OEM (Hitachi) MAF fixed it.

 

[Hall]

Visual inspection is step # 1, yeah ? Hopefully I found the problem....

At first I thought, "nope, that can't be it, it's only for one of the banks but the lower hose actually feeds around to the other bank" so fingers crossed that this is the issue.

Anyone know what this is called in Nissan-speak ? It appears hollow so it's literally just a 3-way coupling.

 

[Puhdantic]

I know in the case of the VQ35DD in our 2019 Pathfinder, unbeknownst to me, I had an ill fitting aftermarket air filter that eventually lead to a MAF code. The air filter would sag in the housing when you clipped it back together, allowing unfiltered air to pass.

That's so interesting. I figured of all the things the aftermarket couldn't mess up, an air filter had to be at the top of the list.

 

[Hall]

Ouch !

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Will have to check salvage yards and probably end up buying most of the air tube/intake assembly and just pull off this piece.

 

[spasm3]

Ouch !

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Will have to check salvage yards and probably end up buying most of the air tube/intake assembly and just pull off this piece.

I might try just an appropriate sized T and see how that works.

 

[Hall]

I might try just an appropriate sized T and see how that works.

That may be what I end up doing. Visually, it appears that (2) of the barb fittings are one size while the 3rd is slightly smaller so that may throw a kink into things.

 

[spasm3]

That may be what I end up doing. Visually, it appears that (2) of the barb fittings are one size while the 3rd is slightly smaller so that may throw a kink into things.

Local Home depot has all kinds of tees, i can't tell the sizes by looking. But they have things like this,

 

[spasm3]

Tons on amazon also, search for " barbed tee" .

 

[michaelluscher]

Visual inspection is step # 1, yeah ? Hopefully I found the problem....

View attachment 99405

At first I thought, "nope, that can't be it, it's only for one of the banks but the lower hose actually feeds around to the other bank" so fingers crossed that this is the issue.

Anyone know what this is called in Nissan-speak ? It appears hollow so it's literally just a 3-way coupling.

Some type of intake air resonator

Check a parts schematic here

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[Trav]

Visual inspection is step # 1, yeah ? Hopefully I found the problem....

View attachment 99405

At first I thought, "nope, that can't be it, it's only for one of the banks but the lower hose actually feeds around to the other bank" so fingers crossed that this is the issue.

Anyone know what this is called in Nissan-speak ? It appears hollow so it's literally just a 3-way coupling.

A simple smoke test would have exposes that in seconds even if it hidden. Cheap and works even with a small compressor.

https://www.amazon.com/AutoLine-Pro-Automotive-Detector-Diagnostic/dp/B07JVT1NG2/ref=sr_1_2_sspa?keywords=smoke+tester&link_code=qs&qid=1652264015&sourceid=Mozilla-search&sr=8-2-spons&psc=1&smid=A39QUDLVDNA8EY&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUExWTBZREJJRTBTMDEzJmVuY3J5cHRlZElkPUEwNjU5MzM3MUlGNTRJWVBCUFQxSCZlbmNyeXB0ZWRBZElkPUExMDMxOTY2NlBMSEROQlFDSjU5JndpZGdldE5hbWU9c3BfYXRmJmFjdGlvbj1jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ==

 

[Hall]

Local Home depot has all kinds of tees, i can't tell the sizes by looking. But they have things like this,

Some type of intake air resonator. Check a parts schematic here

Yeah, I found it after posting and it's ridiculously expensive. It is shown on parts diagrams but isn't called out separately on any that I ran across. I found a salvage yard selling the complete air intake assembly and need to call them today about it. I would need to make sure they include this piece or see if they'll sell it separately.

 

[spasm3]

Yeah, I found it after posting and it's ridiculously expensive. It is shown on parts diagrams but isn't called out separately on any that I ran across. I found a salvage yard selling the complete air intake assembly and need to call them today about it. I would need to make sure they include this piece or see if they'll sell it separately.

I'd try to lengthen the hose or something to take the tension off, so the replacement does not do the same thing.

 

[JTK]

That's so interesting. I figured of all the things the aftermarket couldn't mess up, an air filter had to be at the top of the list.

Right? First time this ever bit me.

Size and sealing looked perfect, but the aftermarket didn't have wire mesh on the clean side. W/out that wire mesh, the filter would sag and open up a gap in the seal.

I also can't explain why my particular 2019 Nissan won't run with the MAF disconnected once warm. It won't even run enough to get you off the road.

@Hall I wonder if you could salvage that broken OEM assembly with some gorilla glue or the likes?

I recently watched a Rainman Ray video where he fixed a coolant leak on one of these dual intake VQ35's on a RWD Infinity sedan. It was a plastic coolant coupling in the rear left of the engine bay that split open just like your assembly.

 

[Hall]

@Hall I wonder if you could salvage that broken OEM assembly with some gorilla glue or the likes?

Currently tape seems to be working but I will never post that picture !! I will NOT leave it this way either. I cleared the code, it's idling correctly (it was idling about 100 rpm higher than typical) while lean. I don't think it can be saved - it was completely broken off. The picture I showed above didn't look as bad because the (3) hoses were kinda holding it close. Plus, the barb is close to 1" long and took some destruction to get it out of the hose.