G 30 Van V8-454 7.4L VIN N TBI (1995)
application) corresponds to full flow.
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Actual or "controlled" idle speed is obtained by the control module positioning the IAC valve pintle. Resulting idle speed is generated from the
total idle air flow (IAC / passage + PCV + throttle valve + vacuum leaks).
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Controlled idle speed is always specified for normal operating conditions. Normal operating condition is engine coolant temperature in
operating range, the A/C is "OFF," manual transmission is in neutral or automatic transmission in drive with proper park/neutral position. A
high or low engine coolant temperature, or A/C clutch engagement may signal the control module to change the IAC counts.
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The minium idle speed is set at the factory with a stop screw. This setting allows enough air flow by the throttle valves to cause the IAC valve
pintle to be positioned a calibrated number of steps (counts) from the seat during normal controlled idle operation.
The IAC counts will be higher than normal on an engine with less than 500 miles, or an engine operating at high altitude or an engine with an
accessory load such as the alternator, A/C, power steering or hydra.boost brakes activated.
THROTTLE POSITION (TP) SENSOR
The Throttle Position (TP) sensor is connected to the throttle shaft on the throttle body unit and is non-adjustable. It is a potentiometer with one
end connected to 5 volts from the control module and the other to ground. A third wire is connected to the control module to measure the voltage
from the TP sensor.
As the throttle valve angle is changed (accelerator pedal moved), the output of the TP sensor also changes. At a closed throttle position, the output
of the TP signal is low (approximately 0.5 volt). As the throttle valve opens, the output increases so that, at Wide Open Throttle (WOT), the
output voltage should be approximately 4.5 volts.
By monitoring the output voltage from the TP sensor, the control module can determine fuel delivery based on throttle valve angle (driver
demand).
