Thinking of Buying 2003 Cavalier

I test drove a 2003 2.2 with 103,000 miles today (Private seller). Very clean inside and out, only problems I noticed were:

1. The car vibrated at idle with the air running, if I shut the air off it stopped. The air was good and cold, and you couldn't notice the vibration at driving speeds, but I'm worried the compressor may die right after I by it any ideas?

2. The oil cap had a slight coating of white film. Internal gasket leak? I changed the LIM on my 2000 Alero last winter and my daughter totaled it this spring. The car is for her.

Any comments are appreciated.

Thanks

well when you turn the ac on in any car it will make it do that, but depending on the idle speed of the car it could seem more or less shaky than other cars, to fix it just increase the idle speed by like 150-200 rpms and you do this at the throtle body cuz my cavy did that but i just changed the idle speed from 600 rpms to about 750 rpms and it fixed the problem.

i dunno about the whole car shaking, but when the ac is on and im idling, my whole dash starts to shake. not bad but its definitely noticeable. nothing to worry about though. cavys are made from pretty cheap materials and u will notice things shaking and making weird noises. i just kinda get used to them.

Upper motor mount is probly blown to hell. My 04 shook all to hell with the ac on when my upper mount took a dump.

Its a 2003 and already has 103,000 miles?

Must be ALOT of highway interstate driving...

My car shakes too when the AC is on, but its barely noticeable...