2003 Ford F150 making ernt-ernt-ernt noise

2003 FORD F-150
106,000 MILES • V8 • 2WD • AUTOMATIC
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THEDIRTYSOUTH
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My F150 is making an loud ernt-enrt-ernt noise when it's running. The noise is intermittent, and happens more when it's cold outside, the engine is cold, or when I change from running the AC to vent. The engine isn't robbed of power and the RPMs do not change when it happens. I have cleaned the MAS sensor, and replaced the air filter based on someone thinking it might be backfiring into the air intake. I have tried to localize where the noise is coming from and it seems to be coming from the driver's side right above or next the wheel well in the engine compartment.
Jul 30, 2008 at 10:27 AM
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2CARPRO JACK
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If someone suggested it is backfiring through the intake, does the noise sound like an echo noise in the intake manifold? If so it is probably the Idle Speed Control Valve. Have seen/heard many of them make a really weird sound in the intake manifold
Jul 31, 2008 at 7:39 AM
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THEDIRTYSOUTH
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Honestly I can't tell if it is an echo or not. It doesn't sound metallic, that's all I can be sure of.

Can I unplug the Idle Speed Control Valve to see if the problem sound persists?
Jul 31, 2008 at 3:11 PM
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2CARPRO JACK
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may still do it.The valve sticks part way and causes the noise. Try unbolting the IAC valve and hold your fingers over the holes in the intake where it goes, May have to keep it running from inside the car, but if that is the problem the noise will be gone
Jul 31, 2008 at 4:09 PM
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THEDIRTYSOUTH
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I couldn't keep it running with the valve disconnected or taken off the intake, so I took a chance and put a new one on. So far, after about 20 miles driven, the noise seems to be gone.
Aug 2, 2008 at 11:58 AM
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2CARPRO JACK
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It is kind of difficult to do. Keep your fingers crossed......lol
Aug 3, 2008 at 7:58 AM