6.5 surging, black smoke

[6.5schoolbus]

Hi everybody, looking for some advice

My Savana school bus started surging when I topped out on a hill. I took it to a shop and they said they got a code for the accelerator position sensor, and fixed a pinched o ring at the fuel filter. I replaced the accelerator assembly.

Now it’s not giving any codes, but idles up and down on its own after start up, putting out black exhaust (which it wasn’t doing before)

[6.5schoolbus]

Cool, thanks for the help y’all

[JohnC]

You didn't give us much to go on.

What year is it? Was there any change between the pinched o-ring and changing the APP? What was the code?

Could be a lot of things. First thing I'd do is check the fuel delivery to the injection pump. Then I'd put a scanner on it and see what the pump is (trying) to do when it's acting up.