Toyota Corolla 1970-1987 Repair Guide

Octane Selector



See Figures 1 and 2

The octane selector is used as a fine adjustment to match the vehicle's ignition timing to the grade of gasoline being used. It is located near the distributor vacuum unit (on models so equipped), beneath a plastic dust cover. Normally the octane selector should not require periodic attention, however should adjustment become necessary:

Click image to see an enlarged view

Fig. Fig. 1: Octane selector

Click image to see an enlarged view

Fig. Fig. 2: Figures shown are actual road speeds

  1. Align the setting line with the threaded end of the housing and then align the center line with the setting mark on the housing.
  3. Drive the car to the specified speed for the octane selector test in High gear on a level road.
  5. Depress the accelerator pedal all the way to the floor. A slight pinging sound should be heard. As the car accelerates, the sound should gradually go away.
  7. If the pinging sound is low or if it fails to disappear as the vehicle speed increases, retard the timing by turning the knob toward R (Retard).
  9. If there is no pinging sound at all, advance the timing by turning the knob toward A (Advance).

On 1973-79 models, do not turn the octane selector more than1/2turn toward R. Do not turn it toward A at all

  1. When the adjustment is completed, install the plastic dust cover.

One graduation of the octane selector is equal to about 10 degrees of crankshaft angle