An ECM controlled VSV is located in-line with the vacuum signal to the PAIR valve. It is a normally closed VSV that is switched on by the ECM during conditions when emission production is high and fresh air is needed to promote emission oxidation. A resonator is located at the air intake and is used to baffle air pulsation that normally occurs during system operation.
PAIR operating strategy varies between different engine applications; therefore, refer to the Repair Manual for exact system operating parameters. An example of a typical program strategy (Truck with 22R-E engine) allows secondary air flow during the following conditions:
• Cold engine operation; when coolant temperature is below 86' F and engine speed is below 3600 rpm
• Deceleration; when either of the following conditions are met:
-coolant temperature above 140'F, IDL on, and vehicle speed above 2 mph -coolant temperature above 140'F, IDL on, vehicle speed below 2 mph, and engine speed above 2,500 rpm
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