If your spark plugs are sooty black, you may have a hole in the accelerator pump diaphragm. This causes a rough running engine at idle from too much fuel going where it is not supposed to go.
I had that happen to me twice. I simply pulled out the throttle cable to raise the RPM high enough to burn the excess fuel and run smooth at traffic lights until I made it home.
Ethanol blended fuel is no friend of YF diaphragms.
