1638. I have a 2005 TE PT with 50k miles. When the vehicle is at idle, the RPM's drop, and the engine shakes and shudders when the A/C compressor kicks on. It actually started doing it when we were using the heat in defrost mode, and now we are using the A/C, and it's happening with that too. The car idles perfectly otherwise. It's just when you hear the compressor clutch engage that the engine shakes. Is it a bad compressor, or could it be that the engine isn't properly increasing RPM's to handle the extra load? – Jon, from Michigan.