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Have a 1999 5.4 4x4 with 205k. I keep getting a p1151. So far I have ran seafoam and changed oil/filter with motorcraft, plugs, replaced bad vacuum lines, and replaced drivers side cats and removed and cleaned t.b. and all vac ports. I cannot find anymore vac leaks. the truck hesitates extremely bad when its cold, you have to floor it to get it to go, after it warms help it gets better but the hesitation is still there, the idle goes up and down too? I am at a lost now any help would be great.
With that many miles on the truck it could be that the O2 sensor is just plain old worn out. P1151 O2 sensor reads lean, bank 2 (drivers side) sensor 1 (in front of the converter)
So i havent got to change to o2 yet due to weather but I did look at the freeze frame and LTFT1 was 0 STFT1 was 3, LTFT2 & STFT2 were the same as 1, however 3 & 4 were both in the high thirties and low forties so I would say I have a problem. will the o2 fix fuel trim that far out of wack?