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.

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