Fix rough idle and stalling on 1986 S10 blazer.only keeps running if pumping gas pedal. was running good and all of a sudden started dying out.

start at the beginning fuel pump pressure at the pressure regulator then look for ignition problems , check mass air flow sensor if equiped

Either not enough air or fuel. Check the air filter and gas filter. Also could be the exhaust system Catalytic converter clogged. No air out, no air in.

Should be on or near the fuel injector supply rail.

an alternator won't stall your car, the battery provides power to keep the spark going. It sounds like you could have some bad fuel, if you're able to run the throttle manually with your foot and keep it going that would indicate idle control. but if it stalls still when you are giving it gas. I would guess a fuel supply issue, either water in your gas, or fuel pump. Good Luck.

I agree with Peter on this one. Sounds like low fuel pressure. First thing is to be sure that you have around 55-60 psi when you turn the key on and running should be around 55. If the pressure drops much below these no.'s the fuel pump may need to be changed. Don't forget to check and/or change the fuel filter also.

Could be several things, a vac leak, dirty throttle body, or faulty idle air control valve.
The computer controls idle speed by how much air enters the throttle body thru the valve.
Usually a vac leak would speed up the engine unless it is causing the rough idle.

Have you checked fuel pressure yet ?

Did you change the fuel filter?

Sounds like a large vacuum leak,low fuel pressure,fuel pressure regulator failure, idle air control valve stuck open,plugged fuel filter.Also check for good consistent blue spark at spark plugs or jumped timing chain.Hope this helps!

Try changing the fuel filter. You may want to consider a Weber carburetor conversion. That Asian carb is old