Spark Control Computer
The computer is located on the air cleaner. The computer consists of 1 electronic printed circuit board which simultaneously receives signals from all data sensors and analyzes these signals to determine spark advance and air/fuel mixture. Incorporated within the computer are the electronics for the throttle control, EGR and air switching systems. After determining spark advance, the computer will operate the engine in 1 of the following modes:
- Open Loop Mode - During cold engine operation, the air/fuel ratio is controlled by information programmed into the computer by the manufacturer. Until normal operating temperature is reached, the air/fuel mixture will be fixed at a rich level to allow proper engine warm-up. During this mode of operation, air from the AIR pump is injected "upstream" in the exhaust manifold to assist in heating up the oxygen sensor.
- Closed Loop Mode - Once normal engine operating temperature is achieved, the air/fuel ratio is controlled by the computer based upon information received from the oxygen sensor.