Ignition Timing

NOTE: Engines are equipped with receptacle for a magnetic timing probe timing meter, located at 9.5° ATDC. Do not use receptacle for timing with conventional light. Timing adjustment is not required on 2.8L (VIN S, W or 9) with Direct Ignition System (DIS), or 3.0L (VIN L) and 3.8L SFI (VIN 3 and 7) engines with Computer Control Coil Ignition (C(3)I) ignition.

CAUTION: Due to late changes and corrections, always refer to tune-up decal in engine compartment for timing procedures and specifications.

Engine must be at normal operating temperature. Turn off all accessories and A/C.
On 4.3L (VIN Z), with TBI, "CHECK ENGINE" light must be off. On all engines, put HEI-EST in by-pass mode by unplugging "Set Timing" connector.
On 2.8L (VIN S, W & 9) with MFI and 4.3L (VIN Z) with TBI, "CHECK ENGINE" light must be off. On 2.8L engine, cooling fan must be off. On all engines, put HEI-EST in by-pass mode by unplugging "Set Timing" connector.
"Set Timing" connector is a Tan/Black wire which breaks out of the engine wire harness near the distributor. On some vehicles, "Set Timing" connector may be on the firewall near blower motor housing. DO NOT unplug 4-wire connector at the distributor. Place Automatic transmission (if equipped) in "D". Adjust timing at engine idle. Clear ECM trouble code after adjustment.
On 3.8L (VIN A), verify if "CHECK ENGINE" light is not on. Disconnect 4-wire connector at distributor. "CHECK ENGINE" light will come on. Place automatic transmission (if equipped) in "D". Adjust timing with engine at idle. Reconnect 4-wire distributor connector. Clear ECM trouble code after adjustment.

IGNITION TIMING SPECIFICATIONS

Application	Degrees BTDC @ RPM
3.8L 2-Bbl. (VIN A)	15 @ Idle
4.3L TBI (VIN Z)	0 @ Idle