I purchased my '99 about 17 months ago with 106,000 miles. When it is cold out (winter) it buzzes loudly at different times...when driving, when parked and idling (which will rev up to about 12-1500 rpm), when stopped and in gear. It sounds like it is coming from the area of the master cylinder area under the hood. Sometimes it buzzes for about 10-15 seconds, othertimes a second or two, usually almost stalling the 4.6l out after. When driving, it stops buzzing sometimes when I push on the gas, other times not. I checked another site and it had one suggestion...that a clip on the rocker arm had come loose. Anyone have any ideas as to what it might be?

 

check youe egr vaccumn regulater
it is mounted on the firewall by the brake booster at about the 10 or 11 o'clock possition.it will have two vac lines runnig to it. may be a bad diaphram in it.. it a shot in the dark and a stretch but it could affect rpm

 

My EGR regulator buzzes after I shut the truck off, if I tap on it with my finger i can get it to stop, no codes, but its kinda goofy.

 

My EVR use to humm a few bars when I shut down at times. I replaced the entire EGR system (not because of that) .. It still humms after shut down at times. I read that it doesn't mean theres a problem - it's a sign you system is pressurizing at it should , nothings wrong.


The noise the OP is hearing is different I think - IMO ,It's either the IAC or a bad PCV valve.

 

i wondered about iac, but don't the rpms usualy go down.

he's prolly gone anyway

well brew did Santa do anything for ya?
prolly not you aint been good!

 

Yea , on a cold start if sticking closed or nearly closed. They will idle real low and might stall . - Just until the 02's take over (about 800 degree's on the first sensor both banks, if I remember right )

Why would he post a question , than leave ? Probably right ..

Haha.. YEA!! - I must have really F'ed up somewhere (still looking) -

I gotta a new credit card bill for Christmas . A traffic ticket for improper use of lights (I had my running light and fogs on - Didn't notice my headlights where off..) - Oh yea, My unemployment ran out...

BUT! someone gave me a lotto ticket for some million dollar drawing tonight - lucks gotta change sometime


BTW - It might be the EGR valve sticking open ..

 

Thanks guys for the info. I'll dig deeper to see if I can locate what it is.

 

hang in there dude! just when it gets darkest the sun somes up.

 

Oh yea , I will and it will eventually

Thanks

 

Sounds like the IAC to me.