Mountaineer 4WD V6-4.0L VIN E (1999)
On applications with air-assisted injectors, the IAC valve also supplies a small amount of air into the path of the fuel injectors. The jet of air causes an
increase in fuel atomization at low speed and light load conditions.
NOTE: The IAC Valve Assembly is NOT ADJUSTABLE and CANNOT BE CLEANED.
The IAC valve (part of throttle body assembly) has an internal diode on some applications. If the internal diode is measured in crossed terminal position
with a digital multimeter, there will be an incorrect or negative reading. It is important that the mating component and harness connectors correctly
oriented. Diagnostic procedures emphasize this importance.
The PCM uses the IAC valve assembly to control:
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No touch start
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Cold engine fast idle for rapid warm-up
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Idle (corrects for engine load)
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Stumble or stalling on deceleration (provides a dashpot function)
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Over-temperature idle boost.
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Air assist to injectors.
Throttle Body Housing
The throttle body housing assembly is a single piece of aluminum casting with an air passage and a butterfly throttle plate with linkage mechanisms.
When the throttle plate is in the idle (or closed) position, the throttle lever arm should be in contact with the Throttle Return Stop. The throttle return
stop prevents the throttle plate from contacting the bore and sticking closed. The setting also establishes the amount of air flow between the throttle plate
and bore. To minimize the closed plate air flow, a special coating is applied to the throttle plate and bore to help seal this area. This sealant/coating also
makes the throttle body resistant to engine intake sludge accumulation.
