P0171 with Landtank's MAF

[NLXTACY]

Ok so I have been rocking the P0171 for a few weeks now and its finally time to take care of it. The usual culprit is the air intake hose but mine was replaced a few months ago and is still totally fine. No cracks at all.

I replaced both of my O2 sensors about a month or so ago after some other CEL codes came up and those went away.

I have not done a fuel injection service recently and my EGR valve is tight.

About a year-ish ago I installed Landtank's MAF. Everything has been fine but because of the new MAF sensor I can't trust the factory specs/pinouts.

Any thoughts here? I want to make sure I'm not missing something obvious before I start replacing everything

 

[landtank]

check for a crack in the Y pipe as well as between the two cats. You're looking for a spot where outside air can enter the system post combustion. Another possibility is a bad connection at the MAF sensor. I've seen this several times. The fix has been to remove the pins and bend the spring tab so it fits tighter.

 

[Ebag333]

Hmm, not sure I'd want to drive around with a P0171 for a few weeks as the code is "system too lean."

From the FSM:

 Air intake (hose loose)
 Fuel line pressure, leak
 Injector blockage
 Heated oxygen sensor malfunction
 Mass air flow meter
 Engine coolant temp. sensor

If the air intake is out, you don't see/smell fuel leakage, your not getting any stumbling or power loss (injectors), then you're down to the O2 sensors or MAF.

My guess would be the MAF as LT suggested.

 

[NLXTACY]

Ok so I inspected every inch of the exhaust and the pipes are all flawless. No cracking whatsoever. So that can be eliminated. I went through and took out each pin of the MAF sensor connector and pushed in the little spring on each one. Gonna go drive around for awhile and see if the CEL pops back up.

 

[landtank]

I came back to edit my first post but will add it here.

I found my bad connection by accident. I was having a lot of idling and running issues and after about 3 hours happened to lightly touch the harness to the MAF and the truck instantly died.

So I'd try that as well. With the truck idling lightly touch and gently wiggle the harness in all directions and see if the engine's idle changes. If the engine's idle does change then the harness is the issue, if it doesn't, I'm not sure that it means it's OK and I'd still check the pins.

 

[NLXTACY]

Well its funny you would mention the idle issue. At idle its just a little bit rough. I went ahead and took it for the drive and sure enough the CEL came on again. I tried playing with the harness like you mentioned. No noticeable difference.

Ugh, I was hoping for something easy

 

[landtank]

another thought would be the fuel pump relay. I had that as well. The NC side of the relay is used normally and gets pitted. The proper way to clean it is with a burnishing tool but I used a new striker from a book of matches.

 

[LXDOC]

suggest you also check all vacuum lines and their connections

 

[OGBeno]

Don't forget about the ECT sensor (3rd one down on the USDS of the head if you are looking straight on the head from the front of the rig). Wire connector might have broken off or sensor bad. EFI section of FSM has a diagnostic for it. It's tough to get too, but if you squeeze your hands through there, move about the PS reservoir, you should be able to work on it with a head lamp.

 

[landtank]

If for some reason you attached the vacuum line to the FPR I'd remove it.

 

[rhyary]

NLXTACY,
I have landtank MAF. It drove fine for months, and then exactly what you described and bad MPG (down to 10)
Per Landtank suggestion, I unplugged the connector and bent the springs a bit to make the connection tighter. Not sure exactly when that was but many months ago.

The car runs great since. MPG back to 11.9 or 12. Smooth idle and NO codes.

 

[NLXTACY]

I haven't had a chance to tackle this yet because I had to leave for work but I have a few days and will see if I can figure this out to close this thread out. Putting this note in to motivate me.

 

[retrofive]

[hijack]

Good to see your still around Joey

 

[NLXTACY]

[hijack]

Good to see your still around Joey

Yeah working in the film industry is completely nuts. Especially doing what I do which only a few people in the world do

 

[landtank]

I was wondering what was going on here. I'm about a week away from a finalized sleeve for the original housing that will require a vacuum line to the FPR. Let me know your progress in case you think this will help.

 

[fzjconvert]

I was wondering what was going on here. I'm about a week away from a finalized sleeve for the original housing that will require a vacuum line to the FPR. Let me know your progress in case you think this will help.

Not wanting to hijack but, I'm having the same issue too! So far I have replaced air filter, replaced vacuum lines, cleared the code and it is back on in about a day and half. Today I cleaned the MAF and bent the springs like you recommended. My mechanic buddy suggested that I change the fuel filter too. Since I have one on hand I am going to do it tomorrow. Then he will clear the the code for me again and see how that goes. Any other ideas?

I have never uncapped or tried to reconnect the FPR after installing your housing and it has been on there for some time so I don't believe that is the cause...

Back round:

The air inlet is newish (inspected good shape)

O2 sensors newish (replaced when I did cats to clear another issue)

No visible signs of fuel or smell.

No sluggishness or hesitation.

Please advise it will help both of us!

 

[turbocruiser]

I'd guess that tightening the connections will work wonders but out of curiosity is your sensor new or used?

 

[fzjconvert]

I'd guess that tightening the connections will work wonders but out of curiosity is your sensor new or used?

My sensor was used... What are you thoughts?

 

[landtank]

the system relies on the MAF sensor giving it consistent readings. So anything that would cause the signal to fluctuate erratically is suspect. That's why I've suggested the connections at the plug.

On the other side, anything that would cause the amount of fuel sprayed by the injectors would be suspect as well.

so look at the Fuel pump relay, pressure regulator and the pump itself. I think that I've read that someone had this problem and a new fuel pump solved the problem.

My manual is with my machinist right now so I don't have it to reference.

 

[fzjconvert]

the system relies on the MAF sensor giving it consistent readings. So anything that would cause the signal to fluctuate erratically is suspect. That's why I've suggested the connections at the plug.

On the other side, anything that would cause the amount of fuel sprayed by the injectors would be suspect as well.

so look at the Fuel pump relay, pressure regulator and the pump itself. I think that I've read that someone had this problem and a new fuel pump solved the problem.

My manual is with my machinist right now so I don't have it to reference.

Agreed! Everything I could find and read last night pointed in that direction. That is why I think my mechanic friend said start with the filter first then I'll start working my way back. I have been wanting to replace the fuel sock anyhow! LOL!