Possible Clues:

• Choke, one of the controls in a car
• It makes the motorist put his foot down
• Accelerator - choke
• You might put your foot down to open this, yet smoother it
• Accelerator used with choke
• Close it and it will stop you for good. Open it and it will speed you up
• Suppress - kill
• Strangle with car pedal?
• One will have to stifle this in your car
• Strangle; fuel controller