Pondering my next step. Either my O2 sensors (246k miles) are bad or I have a vacuum leak no one (incl local dealer and self) can find.

Do I:

Drive two hours to the closest shop with a smoke machine for $100

Change the O2 sensors myself for $100 to $140

If I guess wrong, I will have to do the other anyway

 

twice now I have gotten the P1131 and P1151 no O2 sensor code along with the system lean bank 1&2. Starting to make me lean to trying the Oxygen sensor swap.

anyone have advice on what brand to buy or to avoid?

 

I have read to stick with MotorCraft O2 sensors. Bosch as the second choice.

 

I put my scanner on wife's 00' Navigator which also has the 5.4 engine. The O2 sensors did a smooth sweep between .150 and .897 volts. On the F150 it jumps much more erratic and drops down to .02, .01 and sometimes .000.

Tonight leaving work it was rough until I stopped at the store. Then the rest of the way home it ran like a dream.

Really leaning towards O2 sensor now. and from what I am reading, looks like Motorcraft is the way to go even if the cost is higher.

next day: O2 sensord reading a 'steady' .010 with a few drops to .000 according to what I read online the min voltage should be .200 this would also seem to point at bad sensors

 

almost there...

O2 sensors made a big difference. There is still a slight roughness to the idle but the truck no longer dies and feels much more peppy.

This remaining roughness can come and go while it is sitting at idle.

I am thinking the following possibilities:

1) the still to be found vacuum leak

2) coil over plug unit misfiring due to cold

3) some type of polution control valve messing up

I did unplug the EGR during a rough session and it made no difference. Then I used a hand vacuum pump to manually open EGR and the engine did stumble