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Feb 28, 2003 | 10:27 AM

97fordboy

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weird noises

I have a problem with my 97 f 150 with the 4.6.the pickup runs fine But once in a while i will hear a whinning,buzzing noise and the motor will speed up.I step on the accelarator and let off and it goes away and it runs great.what could be the problem.Driving me nuts.

Feb 28, 2003 | 11:40 PM

Racerguy

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From: BC, Canada

weird noises

Could be a sticky IAC. If you do a search on here you will find info on how to check and clean it. Any particular time it does it? More when it's very cold or anything?

Last edited by Racerguy; Feb 28, 2003 at 11:45 PM.

Mar 1, 2003 | 08:56 AM

97fordboy

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weird noises

Most of the time it does it when it is cold.

Mar 1, 2003 | 10:07 PM

Racerguy

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weird noises

There is a TSB about the throttle sticking in very cold temperatures after a longer run at steady speed. Apparently the PCV freezes up. Does your stick or does it rev up by itself?

Mar 2, 2003 | 10:18 AM

97fordboy

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weird noises

i go out and start the truck and let it warm up for 5 minutes or so.get in and put it in gear to back up.this is when the motor will speed up and you hear whinning ,hissing noise.Step on the gas and let off and it idles normal.it does this all by itself.My son drove the pickup last night and it did this in drive. He has a ford thunderbird with the 4.6 that does the same thing.Seems like it will do this warm or cold.we both have aftermarket air intakes but his did this before he put his aftermarket intake on.Could the intakes be the problem?

Mar 2, 2003 | 11:45 AM

Racerguy

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weird noises

When you put the truck in gear the PCM sees that and will bump up the idle speed so it doesnt stall...that's normal....and more noticeable when it's cold. As for the sound I do think that maybe the aftermarket intakes are making more noise than the stock ones so it's more noticeable now.
Anyone else with any ideas?

Mar 2, 2003 | 02:07 PM

drag79stang

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From: Wisconsin

weird noises

There's no location, so I can't shotgun a 'cold weather' concern at it.
Racerguy's pretty much got it covered, tho.
If the pcv system is OK, (as in updated hose, (i.e. foam wrap recall), and the IAC is in good working order, (which would be my first thought for noise concern/idle flareup), then I'd have to experience it myself for further diag.

From my experience, (again, this is MY experience), I've heard/gotten not alot of help from just cleaning IACs. Usually , (like 99% of time), easier to replace them. Also, you'll find that MOSTof the time, the replacement will be an updated part number.......hint, hint...................