Damn AC issue!!!

Okay, I bought this car when I was 20 from my boss. This car was PAMPERED! I mean new paint and a very expensive list of new parts and replacements. She gave me all of the reciepts to keep track of it's history of repairs and new parts. The only problem (at the time I got it) was that the AC wouldn't work right. It blows cold air, but the damn engine revs up and down every 10 seconds. This is annoying as hell. She told me that she had the compressor swapped out twice, but that didn't work and so I'm here asking for some solution or ideas to correcting this issue.

Thanx in advance!!!

Which year and engine?

Well, it is an '85 Firebird Fuel Injected with a 2.8ltr Engine(V6). don't ask what kind of engine casue it doesn't say, but the mainfold is like 2 parts (a top and a bottom half) if that helps.

2.8 litre.... dam thats small, u sure thats right?

That's the right size my friend. I'll put up a pic of the motor and car when I grab my cam. To make it assuring, it states on top of the manifold 2.8 litre Sucka!!!

That's the right size my friend. I'll put up a pic of the motor and car when I grab my cam. To make it assuring, it states on top of the manifold 2.8 litre Sucka!!!

you know, edelbrock makes a manifold for that set-up...
but as to your A/C problem, it sounds like a vacuum issue, but could be electric.
try pulling the EGR vacuum, while A/C (and engine) running.
did idle still jump?
look through the receipts. any hi-side A/C switches or BARO sensors?
the idle ONLY fluctuates when A/C on right?

Yes his engine IS a 2.8 liter, Camaros and Firebirds used that V6s from 1982 to 1990 when they upgraded the engine to a 3.1 giving it 5 more HP.

You guys rock!!! Thanks for the replies and I'll try out your ideas as soon as I get out of work monday, and yes, the engine only idles up and down when I put the AC on.