Engine Controls - Closed Throttle TPS Specifications
87buick12Bulletin: 88-6E-3
Date: Nov., '87
Ref. No.: 88-016-6E
Corp. Ref. No.: 816502
SUBJECT: TPS INFORMATION AND SPECIFICATIONS
MODELS AFFECTED: 1985-88 BUICKS EQUIPPED WITH LB6 2.8L V-6 ENGINES (VIN CODE W)
Some 1985 through 1987 Service Manual 6E3 Sections covering the 2.8L V-6 PFI engines do not include information on the ability of the ECM to auto-zero throttle position sensor (TPS) reference voltage. Auto-zero can be described as the ability of the ECM to determine a closed throttle position any time TPS voltage is within a specified range (see chart below). As long as the TPS reference voltage is within that range, the system will function properly. This capability is found on all 2.8L PFI engines.
When checking TPS output voltage at closed throttle, there are different specifications for the different 2.8L V-6 applications. "Scan" tools having the ability to also read the throttle valve angle should read 0% when the throttle valve is closed. Do NOT adjust the TPS if the voltage is within the specified range and throttle valve angle reads 0%.
ENGINE/ ACCEPTABLE CLOSED ADJUSTMENT
YEAR MODEL CODE THROTTLE RANGE (VOLTS) SPECIFICATION
1985 Skylark 2.8L (VIN W) 0.35-0.67 Volts 0.55 +/- 0.1V
1987 Century 2.8L (VIN W) 0.35-0.7 Volts 0.55 +/- 0.1V
1988 Century/ 2.8L (VIN W) 0.35-0.7 Volts 0.55 +/- 0.1V
Regal