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. See Fig 2
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- Ensure engine is at normal operating temperature. With A/C off, operate engine at idle speed. Ensure SERVICE ENGINE SOON light is off. Ground ALDL diagnostic connector. See Fig 1 . This causes timing advance control to switch from ECM to HEI ignition module in distributor.
- SERVICE ENGINE SOON light will flash while ALDL is grounded. Connect inductive pick-up timing light to No. 1 spark plug wire. Notch in crankshaft pulley should align with stationary pointer on front of engine. See Fig 2 .
- The mark may fluctuate to each side of pointer, but should be centered on the pointer. This position is 8 degrees BTDC. Loosen distributor hold-down bolt and rotate distributor base to adjust (if necessary).
- To set base timing, a magnetic type pick-up may also be used. Install timing probe in engine block, 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 jumper wire from ALDL connector. Ensure SERVICE ENGINE SOON light stops flashing.