Heated Inlet Air System Operation

Fig. 14 Heated inlet air system. 4-156/2.6L engine:

Fig. 15 Heated inlet air system hose and duct routing. 4-156/2.6L engine:

These systems, Figs. 14 and 15, use a thermostatically controlled air cleaner to maintain a predetermined air temperature entering the carburetor/EFI when underhood temperatures are less than 100° F. By maintaining this temperature, the carburetor/EFI can be calibrated leaner, improve engine warm-up and minimize carburetor/EFI icing. Temperature is controlled by intake manifold vacuum, a temperature sensor and a vacuum diaphragm which operates the heat control door in the air cleaner snorkel.
During engine warm-up, air is heated by a shroud surrounding the exhaust manifold, then the air is piped to the air cleaner snorkel and into the carburetor/EFI. The vacuum diaphragm controls the air control valve which is closed to outside air. Therefore all air entering the carburetor/EFI is heated.
During normal operation, as the air entering the air cleaner increases, the air control valve opens to allow heated air to mix with cold air to keep the air entering the carburetor/EFI at about 100° F.
During wide-open throttle operation or at any time engine vacuum is below 4-6 inches Hg, the hot air duct is closed off allowing only cold air to enter the carburetor/EFI.