Vibration and loud hum at idle

[bluevolume]

2001 XLT SOHC

I've got this really annoying sound coming from somewhere in the truck. It happpens when the engine is warm, in Drive, and stopped. It starts out like a slight vibration in the exhaust, but quickly develops a hummmmmmmmmm that is really annyoing. If I rev it up to around 7-800 it will stop. Only happens at idle.

Anyone else seen this?

 

[BuffaloXplorer]

Sounds like a possible IAC (Idle Air Control) Valve problem, but that is usually not something that occurs ONLY in drive. If you put it in park does it go away?

 

[bluevolume]

I don't think it does it in Park -- I would have to check.

I thought that it might be a vacuum leak, but I can't find one anywhere. I've even resorted to the Ether trick but no luck. I have already cleaned my IAC, I don't want to replace it unless I have to.

 

[bluevolume]

I don't think it does it in Park -- I would have to check.

I thought that it might be a vacuum leak, but I can't find one anywhere. I've even resorted to the Ether trick but no luck. I have already cleaned my IAC, I don't want to replace it unless I have to.

OK -- it does do it in Park also. It happens whenever the engine idles down low, like around 600rpm.

 

[TPLYNCH]

Does it do it if the HVAC system is off, or set to panel (A/C compressor not running)?

 

[bluevolume]

Yes, it does it regardless of what the climate controls are set to.

This thread describes the same problem:
http://www.explorerforum.com/forums/showthread.php?t=110189&highlight=vibration

This might be something that I have to go to the dealer for

 

[KJB]

I'd have to agree with Buffalo. Remove and clean your IAC ( Idle Air Control) Valve with throttle body cleaner.