Engine won't idle smoothly at 350 to 450 RPM
- Vacuum leaks at manifold gaskets, wiper line, or throttle shaft.
- Idling Jet Orifice contains dirt or rust, or is too small.
- Idle Air Adjust Screw is mis-adjusted or too short, collapsing spring before it seats.
- Idling Jet Orifice is too large.
- Throttle Idle Adjustment Screw is mis-adjusted.
- Upper Casting Idle Jet Passage is restricted to Idle throat port.
- Upper Casting Air Adjust Screw Passage is restricted to vent hole.