Rough/Unstable Idle: Carbureted

Ensure idle adjustment is correct.
Ensure sufficient secondary spark is available.
Ensure there are no vacuum leaks.
Verify vacuum hose routing is correct.
Ensure fast idle adjustment is correct.
Check vacuum choke break diaphragm.
Ensure fuel level is at specified mark on carburetor sight glass.
Check PCV operation by clamping hose shut. If problem discontinues, replace PCV valve.
Check EGR operation.
Verify ignition timing is correct.
Briefly remove spark plug wires individually to determine if problem can be isolated.
Verify mixture control solenoid operation is correct.
Check thermostatic air cleaner operation.
Check for fuel percolation.