musician235

I just bought a 92 pickup with a recently new engine but it has very black sooty exhaust enough to leave a black smudge on the ground at idle for two minutes. The previous owner was replacing O2 sensors frequently and finally gave up on the truck.

I ohmed the AFM and it was all within tolerance except for one of the tests where it was about 20 ohms below the tolerance.

I opened up the AFM and dialed it a few notches clockwise to lean it out but now the idle has increased, but there is less black smoke.

When I turn the truck on now, The idle is low, But as the truck warms up it begins to idle surge.

When I unplug the AFM everything begins running perfectly, the black smoke goes away and there is a low even idle. Of course I can’t run it that way because pushing the gas pedal cuts the motor out without the AFM plugged in.

Does the apparent resolution when I unplugged the AFM point to a faulty AFM, or are there other possibilities ?

I am reading a lot of the postings trying to learn everything but have reached a frustration point. any advice would be appreciated

Thanks in advance!