Kids 07 focus w/120k miles has a major interior buzz/rattle. Car idles fine. Seems to accelerate ok. Tires are good, rolls smooth enough. But I swear the dash is going to fall out with light acceleration. I changed the power steering fluid today cause steering was stiff. Got air out, pump is quiet but I was looking n rear view mirror to see if any parts were laying in road. Did Harley build this car? Left and right side of dash buzzes. Drivers door buzzes. Letting of gas seems to lessen buzz. U drive for a bit and buzz seems to come and go. Lousy build quality? Broken motor mount? I found myself letting off gas just to quiet car down. I drove it 6 months ago and it was nowhere near this bad.
See if all the chrome or plastic around the windshield is tight. The hood might even be shaking. You might even have air coming under the front of the windshield.
Not unusual with front wheel drive four cylinder cars, I replace my engine mounts before this becomes annoying.
This is not necessarily due to “broken” engine mounts. Engine mounts become hard with age and sag resulting in a transfer of engine vibration to the body.
Five years ago I was accompanying my son during the purchase of a Mitsubishi Eclipse Spider. During acceleration the dash shook as though there was a hardware store paint shaker attached to it. I told my son no one will want to buy this car so make an offer accordingly. After the purchase I replaced all four engine mounts and the vehicle performed like new.
I had to move coolant tank to reach p/s line and did see motor mount. Reminded me of recent issue on site where mount failed due to “loose” bolts. Might have to do a search for focus motor mount repairs.
A Ford TSB (TSB 08-24-9) for 00-09 Focus models discusses "excessive engine vibration", but says it’s most noticeable at idle and in reverse.
The advice is to check the rear engine roll restrictor for debris (small stones, ice/snow) and remove it if it’s packed in there.
Then after that, there is a shield available (Ford # 2M5Z-16102-AB) that installs to keep out the crud.
Since they do stress (“most noticeable”) at idle and in reverse, I’m not sure this is your problem, but who knows? Thought I’d pass it along, anyhow.
EDIT: link to TSB
wasted some time. picked up a “good” mount at junkyard. several cars had separated rubber mounts but I found a good looking one. my theory was a 2nd mount might be “not bad” vs mine. it takes about 7 minutes to change mount. and the buzz increased about 100%. I couldn’t even drive car due to rattle. put on old one. I did find a loose heat shield next to alternator I changed a few months ago. tightened that up. buzz is less than before.
A new mount would have softer rubber and decrease vibration.
a little awkward to remove mount at junkyard with nothing under motor. the mount than does not want to come out without a little persuasion. I like to look around boneyard just to see what I can find. at least it was above freezing yesterday