K 1500 Truck 4WD V8-350 5.7L (1986)
EGR Control Solenoid: Description and Operation
The ECM controls vacuum to the EGR valve electronically--through the EGR bleed solenoid.
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When the engine is warm the solenoid is de-energized allowing vacuum to the EGR valve.
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When the engine is cold the solenoid is energized blocking vacuum to the EGR valve.
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The solenoid also decreases the amount of vacuum to the EGR valve when the torque converter clutch is engaged.
