Thank you for asking your question on JustAnswer. The most common cause of the problem you are having is a defective IAC (Idle Air Control) valve located on the throttle body of the upper intake manifold (see diagram below), I am also sending you test procedures. I hope this helps you out.
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1. Keep the engine running by giving it just enough throttle to keep it from stalling. 2. With the Idle Air Control (IAC) valve connected, monitor the voltage across the 2 wires at the IAC valve connector. The higher the voltage, the harder the Powertrain Control Module (PCM) is trying to raise the idle. Expect more than 4 volts if the idle is lower than normal. 3. Then, with the engine running at a low idle speed, unplug the connector, and if the RPM does not drop when the connector is unplugged, replace the IAC valve.
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Sorry to hear about the loss of your father, as well as the loss of the family friend.
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