jb2012

I just bought a 2008 f150 extended cab 4x4 with a 4.6 and 140k and I believe my a/c compressor is bad, because when I turn it on at idle the whole freaking truck shakes. What's weird is it doesn't do this every time the a/c is on. Sometimes it idles smooth as a top and sometimes it feels like the doors might fall off. The worst part for me is this buzzing sound it makes when acting up. When I get up around 2000 rpm it buzzes really annoyingly loud; I think the sound is coming from the passenger side by the windshield. I have replaced the a/c compressor on the last two trucks I've owned and I want to put this one off as long as possible as these 4.6 compressors are a major pain in the ***. Is there something in the cab I can tighten to make that buzzing sound stop? Its driving me CRAZY especially since I JUST BOUGHT the dang thing.

Eric0508

I would clean the throttle body, MAF, and replace the fuel filter. Then do the idle relearn process to see if that clears up your shaking at idle

The buzzing might a loose piece of trim or maybe one of your pulleys is starting to go out. have someone rev it up and try to pinpoint where it is coming from