GLC With A/T

Disconnect hose between anti-afterburn valve and air cleaner, at the valve. Start engine and run at idle. Place finger over hose (intake port). Engine speed should not change.

Fig 1: View of Anti-Afterburn Valve Intake port on GLC models differs in design.
Increase engine speed and quickly release accelerator. Suction should be felt at air intake port. If no suction is present, or if suction lasts for more than 3 seconds, replace anti-afterburn valve.