Chevrolet Chevette/1000 1976-1988 Repair Guide

Models with EST Distributor


Engines with Electronic Timing (EST) can be identified by the absence of a vacuum and a mechanical spark advance on the distributor. EST allows continuous spark timing adjustments to be made by the ECM (Electronic Control Module).

  1. Follow all instructions on the Vehicle Emissions Control information label located on the radiator support panel.
  3. Connect the pick-up lead of the timing light to the number one spark plug. Use a jumper lead or adapter between the wire and plug, better yet use a timing light with an inductive type pick-up.

Do not pierce the wire or attempt to insert a wire between the boot and the wire. Connect the timing light power leads according to the manufacturer's instructions.

  1. Start the engine and make sure it is operating at normal operating temperature.
  3. Increase idle and disconnect the four (4) terminal EST connectors at the distributor. This will cause the engine to operate in the bypass timing mode.

Steps 3-4 are important, because if the engine is at idle and not warm enough, when the EST terminal is disconnected, the oxygen sensor could cool off, putting the system into an open loop operation resulting in the engine shutting off.

  1. With the engine running, aim the timing light at the timing mark.
  3. If a change is necessary, loosen the distributor hold-down clamp bolt at the base of the distributor. While observing the mark with the timing, slightly rotate the distributor until the correct timing is indicated. Tighten the hol-down bolt, and recheck the timing.
  5. Turn off the engine and reconnect all wires.

Models with air conditioning require removal of the compressor since it is mounted directly above the distributor.

Do not disconnect the refrigerant lines. Move the compressor and bracket to one side.