flapping? rattling?

[Shaolin]

my friend's focus sounds like there's something flapping or rattling when she gives it gas.. we'll be idling, she steps on the gas and the rattling/flapping starts.. i can't seem to pinpoint the sound but any ideas what it'd be? it just happened recently.. there's nothing caught under the car or anything but like i said i can't seem to pinpoint the source of the sound.. when she gases it, it just starts flapping.. anyways, i hope that's enough information because i don't have any other info to give.. sorry.

[7thgenvic]

might to with your tires or something, because if the sound is not occuring when the engine is idling, and the sound isnt' comming from the engine, may be to do with tranny?

thats my guess,

[t3rry]

could be the lifters, chekc the oil

also try revving it in park or neutral and see if it still does it when you aren't moving

[sputnik]

Try running a higher octane fuel or check your timing. You may be experiencing "pinging" which is when the sparkplugs arent insync with the fuel supplied to the combustion chamber.

[DBFORDTECH]

Hi

Does it make the noise in gear or can it just be revving in park/neutral. Do you have to be moving?
Does the noise change with road speed?

Focuses tend to break their EGR tubes, check it...But it makes an obvious exhaust noise under the hood, not a flapping.

[carmex]

Do you think it's near the front or the rear of the vehicle?