GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide

Controlled Combustion System



The CCS system relies upon leaner air/fuel mixtures and altered ignition timing to improve combustion efficiency. A special air cleaner with a thermostatically controlled opening is used on most CCS equipped models to ensure that air entering the carburetor is kept at 100°F (38°C). This allows leaner carburetor settings and improves engine warm-up. A 15°F higher temperature thermostat is employed on CCS vehicles to further improve emission control.


Since the only extra component added with a CCS system is the thermostatically controlled air cleaner, there is no additional maintenance required; however, tune-up adjustments such as idle speed, ignition timing, and dwell become much more critical. Care must be taken to ensure that these settings are correct, both for trouble free operation and a low emission level.