it says left bank and right bank running lean...what should i do and has anyone ever had this problem...thx

 

My 4.6 started that after I put the high flow throttle body and air filter on it. The computers on these trucks will adapt to changing engine conditions, such as both banks lean, and will compensate for any mods you have done. That being said, you may need an adjustable fuel pressure regulator or bigger injectors. I need to do one of the two because my truck pings on anything under midgrade. Just take it to autohell or someplace and get the light reset. It may take a couple three times, but the computer will eventually adjust. At least that's what the parts manager at the local stealership told me when I asked about injectors or something.

 

check for vac. leaks first could also be a bad m.a.f.s.

 

• 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

http://www.obd-codes.com/trouble_cod...gen-sensor.php

 

Its a bad Mass Air Flow Sensor. We just had the exact same problem on our 98 navigator with a 5.4 (same codes) Cleaning it didnt help. The new MAF sensor from autozone was $89 with core exchange and it fixed our problem.

 

The most common cause of P0171 and P0174 codes together is due to a vacuum leak, not the MAF or any other sensor.

The most common reason on these trucks is that cheap-*** vacuum elbow located on the PCV tube that runs around from the passenger-side valve cover back around behind the engine where it connects to the intake next to the IAC.

If the elbow is bad, you can pick up a replacement tube with elbow at the Ford dealer (they'll have plenty in stock) or you can replace the elbow itself. Someone posted awhile back that they used a simple 90-degree spark plug boot as a satisfactory replacement...

Steve

 

checked and sprayed all vaccuum line with no leaks. everything checked out. i reset the light with a scanner tool 3 times but it keeps coming back on. i will clean the maf sensor and see if that helps-if it doesnt i will replace it...any other info? thx a bunch

 

Also check all the vacuum lines that run up against the firewall and have a elbow that connects to the back of the throttle body. Also, change your fuel filter and clean your fuel injectors.

 

Go back and check ALL the elbows on that PCV line.

Very, very common....

Steve