There is a loud humming noise from the air. Intake box and RPMs jump around in neutral

Tiny
MISCHKA85
  • MEMBER
  • 2000 MERCURY COUGAR
  • 138,000 MILES
I have just replaced the throttle position sensor and the idle air. Control valve, I have replaced the iac 4 times within 5000 miles, voltage to the iac is normal and cpu is not throwing any codes, there is still a loud humming from the air box and rpms jump around a little while in neutral
Thursday, September 22nd, 2011 AT 11:55 PM

1 Reply

Tiny
DRCRANKNWRENCH
  • MECHANIC
  • 3,380 POSTS
Check the rubber mounts for the airbox as well as the seal of the air filter. There is also a box under the front of the intake called a resonator. It is made to make the intake quieter, but if it is loose or has come off the air tract, it wil make a noise. It is like blowing air over the top of a soda bottle. Just at 50MPH.
Also check the air tract in genral from the air filer to the intake by removing the clamps and looking down it with aflashlight and checking for cracks.
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Friday, September 23rd, 2011 AT 12:22 AM

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