Service engine soon light flashing when going up hill or highway
my 4.3 v6 4x4 runs fine around town,
or in any slow conditions really. But
when I climb a steep hill and try to
go 55 my light comes on and I lose
some power, give or take a minute it
clears up and runs fine like nothing
happened and light turns off. Need
help on this have no clue what it
could be, I have cleaned my mass air
flow, changed plugs and wires, just
did a fuel pump and new fuel filter
and still acting up.