i'm back with a different question that may be related to my other previous ones about tune ups. i noticed that when i have the A/C off, the little "dip" in the engine doesn't happen, and when it's on, it does. i had the compressor replaced last summer. would my little dip in the engine have more to do with the A/C than needing a tune up? i live in SoCal so the A/C is pretty important.

Normal, it is the compressor kicking in.

This is what you want to happen.

no, it's not the compressor. i know what that's supposed to sound like. this is definitely the engine dropping from 600 to 400 rpm every few seconds when the A/C is on. it's never done this until the last week.

Compressor is probably faulty and the refrigerant is low.

Every couple of seconds is the compressor trying to compensate for low R134a.

Take it to the shop which replaced it and ask if they actually put any oil in with the refrigerant.