Home Porsche Repair Porsche 911 Carrera (964): 1989-94 Technical Data-Without Guesswork
Idle mixture
Adjust idle mixture (%CO) with 3 mm Allen wrench. 
Turn screw clockwise to richen mixture.
Turn screw counterclockwise to lean mixture.
Adjust mixture with engine not running in order to avoid bending sensor plate arm.
Make small adjustments. Remove tool before starting engine. Raise engine speed a few times before rechecking mixture.
When finished, check sensor duty cycle using Bosch Hammer (Porsche tester 9288) at diagnostic plug.
Oxygen sensor
Duty cycle.....20% - 80%
25 CIS Fuel Injection
page 25-9
Idle mixture
Adjust idle mixture (%CO) with 3 mm Allen wrench.
  • Turn screw clockwise to richen mixture.
  • Turn screw counterclockwise to lean mixture.
  • Adjust mixture with engine not running in order to avoid bending sensor plate arm.
  • Make small adjustments. Remove tool before starting engine. Raise engine speed a few times before rechecking mixture.
  • When finished, check sensor duty cycle using Bosch Hammer (Porsche tester 9288) at diagnostic plug.
    Oxygen sensor
    Duty cycle.....20% - 80%
    25 CIS Fuel Injection
    page 25-9