Interesting problem. 1997 Ford F-150, 5.4 L, Auto., 2WD, Regular cab, Long bed. Few months ago computer kicked out a P0171 code. Changed the MAF and 3 weeks later the code came back. Then replaced the O2 sensors on bank 1. Few weeks later code comes back so ran 2 cans of fuel injector cleaner and a few weeks later the code comes back. Changed the PCV and 5 days later (today) the code comes back again. So ok, now what??? Any suggestions where to go next?

 

Basically this means that an oxygen sensor in bank 1 detected a lean condition (too much oxygen in the exhaust). On V6/V8/V10 engines, Bank 1 is the side of the engine that has cylinder #1.

A code P0171 may mean that one or more of the following has happened:

The MAF (Mass Air Flow) Sensor is dirty or faulty. Note: The use of "oiled" air filters may cause the MAF to become dirty if the filter is over-oiled. There is also an issue with some vehicles where the MAF sensors leak the silicone potting material used to protect the circuitry.

There could be a vacuum leak downstream of the MAF sensor.

Possible SolutionsPossible solutions include:

In the vast majority of cases, simply cleaning the MAF sensor does the trick. Consult your service manual for it's location if you need help. I find it's best to take it off and spray it with electronics cleaner or brake cleaner. Make sure you are careful not to damage the MAF sensor, and make sure it's dry before reinstalling

Inspect all vacuum and PCV hoses, replace if necessary

Check for a dirty fuel filter and proper fuel pressure

 

Sounds like a plan. I will try that this weekend and see what happens.

Thanks for the help.

 

no problem let me know how it goes

 

Cleaned the MAF and replaced a few vacuum lines. Code is staying off for now, but it usually takes a few weeks to come back. Will keep you posted. Thanks again for your help.

 

Ok.....light stayed off one week and came on again this morning. Last weekend I took out the MAF, took it apart and cleaned it with electronic contact cleaner. Then I replaced a few suspect vacuum lines. Any ideas of what to try now??? Should I test the O2 sensors I replaced in case I happened to get a bad one?

 

Are you using a after market aircleaner like K&n? Checking your o2 sensors will not hurt

 

Nope, using stock replacement Fram filter. Think I have found the issue. Buddy of mine looked it up on-line in the Mitchell Manual and they show the number one cause for the 0171 code on the 5.4L engine being a leaking intake gasket. So next weekend I am going to replace the gaskets and the $12 sensor in the manifold. Will let you know how it goes.