Throttle body balance and idle setup

On a multi-cylinder engine, unbalanced throttle bodies mean each cylinder pulls a different amount of air. The result is a lumpy idle, a surge at constant throttle, and vibration through the bars.

What we do

• Vacuum measured on each cylinder with a manometer
• Bodies balanced to within spec of each other
• Idle speed set to the manufacturer figure
• Throttle cable free play set
• Air filter and intake condition checked, since a blocked filter changes everything
• Vacuum lines and manifold rubbers inspected for splits
• Adaptation reset and relearn run where the ECU uses one

Worth doing at every full service on a four-cylinder, and worth doing before anyone writes you a calibration.