Firebird V8-305 50L VIN F FI (1987) - ESC System Functional Check Update
Electronic Spark Timing: Technical Service Bulletins
ESC System - Functional Check Update
Number 87-6(Gasoline)-70
Date 9/87
FUNCTIONAL CHECKING THE ESC
Subject:
SYSTEM - SECTION 6E1
1986 BONNEVILLE AND 1986-87 GRAND PRIX AND FIREBIRD MODELS WITH A 5.0L ENGINE (VIN H)
The following page and chart in this bulletin are to be used in place of the charts in the 1986-1987 Service Manuals for the subject vehicles.
The change in the chart is the addition of the vehicle speed input to the ECM requirement. The ECM will not retard timing if a mph input is not received.
The new step is to lift drive wheels and run engine above 850 rpm and drive wheels turning minimum 20 mph. If the ESC is functioning properly, an
engine rpm drop will be noticeable via a "Scan" tool or tach.
CHART C-5ELECTRONIC SPARK CONTROL (ESC) 5.0L (CARB)
Circuit Description:
If the timing is retarded at idle, it may be due to ESC operating. ESC should not operate unless a knock is present, and vehicle speed is above 20 mph.
