Hi,

I am new to this forum, but not new to repairing cars. I am receiving error codes for both the right and left bank O2 sensors. My fist action was to clean the MAF sensor. Still codes after the clean. I then replaced it. No luck. I then replaced both O2 sensors. Still no luck. I then took it to a shop and had them smoke the engine and ensure there were no air leaks. Non found. What should I check next?

Fuel filter?
PVC valve?
Something else?

 

Both of those things, and it usually is a vacuum leak that causes both banks to go lean, get a can of carb cleaner and spray all around the intake tube connections, intake manifold and check out the rubber boot that goes from the PCV hose to the valve, a lot of times it gets messed up and holes in it and leaks there. Misfires can also cause lean codes, but you'd probably know it if you had misfires on both banks, as your truck would run like crap.

Post your year/model/motor so we know exactly what we're dealing with please.

 

2002 F150 v6

I don't receive any misfire codes and yes it runs a little rough.

 

http://www.sparkys-answers.com/2009/...and-p0174.html

Try not too rub the filament like he says...

Use a mild electronics cleaner...

 

Thanks Guys. I will try these things over the next week and keep you posted.

 

I'm back. I ended up replacing the fuel filter and cleaning the Mass Air Flow Sensor. I also verified that I do not have air leaks. What should I do next? Should I shoot for the EGR valve? I am not getting a code for it.

I can hear a ping when I drive and its a little rough on idle. The codes am I getting are System to lean (Bank 1 and Bank 2)

 

The 4.2l in those years had problems with the isolation bolts for the upper plenum. Most likely needs bolts and orings! There are two pieces to the upper plenum. When you have the upper plenum off check the intake manifold runner clips in the back of the engine and clean the egr ports in the lower intake.