Transmission Controlled Spark (TCS) System

Used on all 1975-79 6-cylinder, V8 Calif, vehicles, and some 1978 Federal vehicles, this system reduces NOx emissions by helping lower peak combustion temperatures during high engine load conditions. Vacuum advance is allowed only in high gear (Man. Trans.) or above 36 MPH (Auto. Trans.). System uses the coolant temperature override switch, a solenoid vacuum valve, and a solenoid control switch and a vacuum spark control check valve.

Fig 1: 6-Cylinder Engine TCS System

Courtesy of AMERICAN MOTORS/RENAULT CORP.

Fig 2: V8 Engine TCS System

Courtesy of AMERICAN MOTORS/RENAULT CORP.

Fig 3: 1975-77 V8 Engine Spark CTO System

Courtesy of AMERICAN MOTORS/RENAULT CORP.