Hey folks. I've had the wonderful fun of cleaning the EGR ports and throttle body over the weekend. They were kind of gommed up, but not too bad. However, that didn't take care of the problem. The CEL is back on, and it's running the same codes, "lean on bank one and lean on bank two". I also cleaned the Maf sensor. How can I tell if the Maf is bad, or know which O2 sensor is bad, the upstream or downstream? The truck has a lot of spark knock, and at about 3000rpm, smothers down really bad.
Any help is appreciated.

 

Sounds like either a vacuum leak or a clogged fuel filter. I would check the EGR hose assembly, they are known to crack behins the intake in the elbow.
Usually if the MAF is too far out of spec, it will give it's own code.
You might want to check the fuel pressure. It sounds to be starving for fuel from either a weak pump or a clogged fuel filter.
The front sensors are the ones that read the rich or lean condition.
Bank 1 (passenger side) Bank 2 (drivers side) Sensor 1 is before the converter closest to the engine Sensor 2 is after the converter.

 

Check the PCV hose that runs form the right side valve cover to the back of the engine. The rubber deteriorates where it plugs into the intake manifold in the back of the engine. Will cause lean codes for both banks. Chances are, that's your problem. I've replaced many. Cheap fix. Your local Ford dealer probably stocks them.

 

Thanks fellas! I already changed the fuel filter and checked the pressure, normal. I'll check the pcv hose and the other things you mentioned. It's also almost time to change plugs and wiring....can't wait for the fun of that.
Thanks for the info on which O2 sensor, I'll just have to keep working at this. By the way, could a malfunctioning catalytic convertor be causing this problem of smothering? I had an old car that the cat clogged up and smothered the engine down...just a thought.

 

I had the same problum codes. I cheaked averything. It was the fuel pump.I cheaked the presure and it was at 30. With the vac off it was 42. It was running on the low end but still with in spec. Its not a cheep fix but it did fix it.







98 F-250 supper 4x4 short 5.4