General System Description

Fig. 1 PGM-CARB Inputs & Output:

The PGM-CARB system used on 1988 Prelude is a feedback system which, unlike previous models, has a self-diagnosis function. When an abnormality occurs in a signal from one of the inputs, Fig. 1, the control unit lights the PGM-CARB warning light, stores the failure code in erasable memory and indicates the code with a LED on the control unit anytime the ignition in on. When the ignition is initially turned on, the control unit supply ground for the PGM-CARB warning light for approximately 2 seconds.
This system also controls the carburetor, fuel supply system and air intake system, as well as the electronic air control valve and other emission systems.
This system incorporates a fail-safe function. When an abnormality occurs in signal from one of the inputs, the control unit ignores that signal and assumes a pre-programmed value that allow the engine to continue to run.
The system also incorporates a backup function that, when an abnormality occurs in the control unit itself, allows a backup circuit independent of the system to permit minimal driving.
This carburetor system consists of two side draft carburetors, each of which has a variable venturi. These carburetors allow for a smooth increase of engine speed and engine output due to change in venturi area in proportion to carburetor intake air flow rate.