89 s-10 2.5L runs rough, occasional backfire

[stonevito]

I have checked timing, pcv, new plugs, wires, cap, rotor, cleaned carb. New fuel added, fuel filter. It looks like it is running too rich (can see gas dancing on carb butterfly when running. It runs fine at highway speeds. Chokes, skips and occoasionally backfires when slight acceleration. Check engine light not on, so no diagnostic codes.
I can't find any fuel mixture screw on carb. Wouldn't dummy light be on if O2 sensor, map sensor, ecm, etc. are bad?

[jackass#1]

check fuel pressure. did you disassemble the carb or just sprayed cleaner in it? may want to get rebuild kit or gasket set and clean each piece. check for vacuum leaks. hope this helps a bit.

[stonevito]

I sprayed carb cleaner in and also disaaembled the fuel mix assembly on the pass. side of the carb and cleaned it, but I did not totally dis-assemble the carb. I guess that is the next step.
Could the computer be bad if the "check engine" light is not lit? I have had two bad computers over the past 17 years in the truck.
Thanks for the advice.

[Cam1959]

On mine I think there was an adjustment screw on passenger side of carb, bottom, in behind throttle mechanism, hard to see or get at. I think I had to use a 2" slot screwdrivr for it.

I presume you have looked at where your choke valve is when cold and warmed up. Being sure the vacuum lines everywhere have no leak, allowing full vacuum and vacuum timing advance ?

Choke adjust is 3 screw round black thing on driver side of carb. My tab is aeound 2 or 3 oclock position. Mine was sticking once so i opened that to inspect and lubricate coil spring.