Check Engine Light

[PWD4R]

Today I got that dreaded light on the last 10 minutes of my drive back home. I got it checked at auto zone and it said "P0171 Fuel System too Lean (Bank 1)"
I got gas where I usually do and ran through my tank from full to empty today from off roading and the commute. Engine definitely took in some dust this weekend and I had a few off camber/sideways moments so that may contribute idk. Auto zone dude too me to give it a few days to see if it goes away.
Do you think this is simply just a dirty MAF? I haven't looked at it but I would be surprised if it's not the original one for the last 223k miles.

Also he recommended to try to put fuel system cleaner in it.. idk how I feel about all that though. Any advice?


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[turbo8]

Clean the maf and check for vacuum leaks before buying replacement parts.

 

[mtbtim]

I can't guarantee it, but what [MENTION=94914]turbo8[/MENTION] told you is sound advice and the MAF is the culprit. I would clean the MAF sensor first and replace the air filter as well. I got the same code after driving a lot of dusty dirt fire roads and cleaning the MAF cleared up the problem.

If you haven't removed the MAF sensor before to clean it, it's attached to the air tube. You can either remove the air tube so it's easier to get the two phillips head screws off, you could move the cruise control unit out of the way so you can get a traditional screwdriver in there or maybe use one of the special low-profile ratcheting screwdrivers. My preference has been to move the cruise control unit out of the way.

I would not bother with the fuel system cleaner.

The video [MENTION=102606]infamousRNR[/MENTION] and I made for the valve cover gasket replacement included cleaning the MAF. Go to 5:32 play time and you'll see how we cleaned it.

<iframe width="560" height="315" src="https://www.youtube.com/embed/N5fAXAuGozI" frameborder="0" allowfullscreen></iframe>

 

[PWD4R]

I can't guarantee it, but what [MENTION=94914]turbo8[/MENTION] told you is sound advice and the MAF is the culprit. I would clean the MAF sensor first and replace the air filter as well. I got the same code after driving a lot of dusty dirt fire roads and cleaning the MAF cleared up the problem.

If you haven't removed the MAF sensor before to clean it, it's attached to the air tube. You can either remove the air tube so it's easier to get the two phillips head screws off, you could move the cruise control unit out of the way so you can get a traditional screwdriver in there or maybe use one of the special low-profile ratcheting screwdrivers. My preference has been to move the cruise control unit out of the way.

I would not bother with the fuel system cleaner.

The video [MENTION=102606]infamousRNR[/MENTION] and I made for the valve cover gasket replacement included cleaning the MAF. Go to 5:32 play time and you'll see how we cleaned it.

<iframe width="560" height="315" src="https://www.youtube.com/embed/N5fAXAuGozI" frameborder="0" allowfullscreen></iframe>

Thank you. I will watch that. And to the above responder thank you too.


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[PWD4R]

One more question though. Do you think the fuel really is running lean or is the sensor just probably thrown off?


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[mtbtim]

The fuel mixture is running lean because the MAF sensor is sending bad info to the ECU. When the sensor wires in the MAF sensor get dirty, the computer thinks there's less air flow, when there really isn't, so it trims the amount of fuel accordingly. The result is a "Too Lean" fuel mixture (Too high of an air to fuel ratio). A lean mixture means there's not enough fuel. A rich mixture means there's too much fuel.

Clean the MAF sensor wires and you'll be back to normal.

 

[PWD4R]

The fuel mixture is running lean because the MAF sensor is sending bad info to the ECU. When the sensor wires in the MAF sensor get dirty, the computer thinks there's less air flow, when there really isn't, so it trims the amount of fuel accordingly. The result is a "Too Lean" fuel mixture (Too high of an air to fuel ratio). A lean mixture means there's not enough fuel. A rich mixture means there's too much fuel.

Clean the MAF sensor wires and you'll be back to normal.

Thank you for the information. I don't know too much about all that so I appreciate the details.


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[JayRolla]

Also remember a major vacuum leak post maf can cause leak condition when drawing in un-metered air.

 

[68ChargerJMP]

I have been swapping MAF sensors in and out lately. Being a 97, my 4R has the old style MAF. I put in a used old style MAF, ran fine, but would always throw the P0171 code. Odd thing is, I could tell when it was about to throw a code, because I could smell it running rich. Does the ECU try to compensate for the lean mixture and add fuel? It doesn't seem logical for it to smell pig rich when it is supposedly running lean. By the way, I tried to clean that MAF, but the code wouldn't stop popping up, so I just swapped to a newer style MAF.

 

[JayRolla]

I have been swapping MAF sensors in and out lately. Being a 97, my 4R has the old style MAF. I put in a used old style MAF, ran fine, but would always throw the P0171 code. Odd thing is, I could tell when it was about to throw a code, because I could smell it running rich. Does the ECU try to compensate for the lean mixture and add fuel? It doesn't seem logical for it to smell pig rich when it is supposedly running lean. By the way, I tried to clean that MAF, but the code wouldn't stop popping up, so I just swapped to a newer style MAF.

I believe what happens is your truck is misreading the air intake. Adds fuel so it smells rich. Once the fuel trim maxes out the code is thrown.