skylardog123

I have a 97 f150 4.6, when i press the throttle maybe 1/4 of the way down, i hear a squeal kinda like one of those 12000hz frequency sound things, its not loud but the high frequency is ear piercing, any ideas

Fordrocks689

Do you have a aftermarket Air Intake installed?
Even with a stock air box they make noise but it's really noticeable with aftermarket intakes like K&N

skylardog123

Yes, i have a k&n airfilter but my truck has never used to do it, i juat noticed it started doing it one day as i was on my qay home, and its not a whine or anything, its kinda like a very very high pitched dog whistle

Fordrocks689

Sure it's not coming from your speakers? Maybe interference from recent work done? My truck does it but I've experienced it with many trucks with a aftermarket intake.

Only other thing I can think of is speaker interference??? Maybe someone els has had experience with this.

skylardog123

Not the speakers, again it comes when the throttle is maybe 1/4 of the way down and it sounds as its coming from the footqell

white89gt

You don't give a lot of info.... although it appears that you own an oscilloscope. If you hold the pedal at 1/4, does the sound stay persistent? Does the sound change when the truck shifts? Do you have a phone you could make a video?

Jbrew

Is your RFI capacitors good? Check the wire make sure it isn't severed. They break right at the capacitor. They are under the hood, 2 of them. Either they ground to the front or the engine or to the upper intake manifold (if it's metal).

skylardog123

I would record it but my phone wont pick it up, its like quiet, but its so high pitch it hurts your ears, the sound stays consistent with the throttle at around 1/4, anything more and the sound stops, not exactly sure what the capacitor thing is or where its at, and the speakers have been checked since i posted this, doesnt seem to be the problem since its connected with throttle

Jbrew

Can't miss them, they are rectangular capacitor blocks fastened to the engine where I said earlier. They are also called radio noise suppressors. Not only for radio noise, but they keep your other electronics from screaming as well.

skylardog123

How do i check to see if there bad if there is a way,