Pontiac Fiero 1984-1988 Repair Guide

Ignition Timing


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Fig. Fig. 1 Ignition coil terminal identification-1984 2.5L engine with a HEI/EST distributor

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Fig. Fig. 2 HEI/EST distributor terminal connections-1986-88 models


The tachometer (Tach) terminal is next to the ignition switch (BAT) connector on the distributor cap on the HEI systems.

Never ground the TACH terminal; serious module and ignition coil damage will result. If there is any doubt as to the correct tachometer hook-up, check with the tachometer manufacturer.


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Fig. Fig. 3 Location of the ignition timing marks on vehicles equipped with HEI distributor systems

Do not come in contact with any spark plug wires while the engine is running. 20,000-30,000 volts are passing to the spark plugs with engine running.

  1. Connect a timing light to the No. 1 spark plug wire according to the light manufacturer's instructions.

Do not pierce the spark plug wire to connect the timing light.

  1. Follow the instructions on the underhood engine decal for checking the ignition timing. These reflect the latest production changes for your vehicle.

The ignition timing for the Direct Ignition System (DIS) is controlled by the electronic control module ECM and is NOT adjustable.

  1. Disconnect the 4 terminal connector at the distributor.
  3. Start the engine and run it at idle speed.
  5. Aim the timing light at the degree scale just over the harmonic balancer.
  7. Adjust the timing by loosening the securing clamp and rotating the distributor until the desired ignition advance is achieved, then tighten the clamp.
  9. Loosen the distributor retaining bolt. On some engines its necessary to slide the clamp back slightly. Do not remove the retaining bolt.
  11. To advance the timing, rotate the distributor oppositethe normal direction of rotor rotation. Retard the timing by rotating the distributor in the normal direction of rotor rotation.