Ignition Timing
NOTE:
The ECM cannot read base timing. If base timing is incorrect, spark advance curve will be incorrect. Base timing may be set using either a timing light or magnetic timing probe.
- With engine at normal operating temperature and A/C off, run engine at normal idle speed. Ensure Service Engine Soon (SES) light is off. Ground the diagnostic terminal at ALDL test connector. This causes timing advance to switch from ECM control to the HEI ignition module in the distributor. See Fig 1 .
- Notice that the SES light will flash during the time the ALDL is grounded. Connect an inductive pick-up timing light to coil wire or spark plugs No. 1 or 4. Notch in crankshaft pulley should be in alignment with stationary pointer on front of engine. The mark may fluctuate to each side of pointer, but should be centered on the pointer. This position is 8 degrees BTDC. See Fig 2 . Rotate distributor base to adjust, if necessary.
- On 1.6L engines, a magnetic type pick-up may also be used. Install timing probe in engine block, located just below oil filter. See Fig 2 . With engine at normal idle, set timing to 10 degrees BTDC. Rotate distributor base to adjust, if necessary.
- Remove the jumper wire from the ALDL connector. Ensure SES light stops blinking.