My bet is that you have developed a vacuum leak somewhere. I base this on the fact that you are not getting much of a response from adjusting the mixture screw. It should absolutely not run with it all the way in.
Another possibility is the following.
What is your RPM when you adjust the mixture screw? If the Idle is set too high, the throttle plate is open past the idle circuit hole, creating a scenario where adjusting the mixture screw causes little to no change in how the engine runs.
Last edited by 52Carl; 05/11/2020 1:26 AM.
