2 people reported this problem
Abnormal sound from engine on Ford Crown Victoria
Hooting, moaning sound similar to ship's horn or foghorn coming from engine. Sound initially only happens for brief periods during warm up, but then occurs during driveaway & while idling at red lights, stop signs, etc. Sound originates from the IAC Tube that connects the Idle Air Control Valve to the air intake tube. Fix is addressed in Ford Article 94-22-4. Problem is the factory IAC Tube. Original tube needs to be replaced with a re-engineered one that has a 'silencer'/'muffler' built into it. The new part number is F5AZ-9H308-A.
1999 Ford Crown Victoria 100,000 mi, Visitor