Dynasty L4-153 2.5L SOHC (1988)
Heated Inlet Air System: Description and Operation
Fig. 13 Heated inlet air system. 1986-88 4-135/2.2L & 4-153/2.5L engines w/EFI
These systems, Fig. 13, 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.
