idle problem

[iHEARTfcs]

Hi,
I'm new to the forums.

Anyways here's the story, I brought my car ran fine, never had any idle problems or anything. I was unemployed for a while and needed money. Someone was interested in buying my car and offered to pay to take it to a shop and get a check up.

Everything was pretty much fine except for shocks going bad and i need new gaskets between my exhaust piping.

Anyways as we were paying the mechanic pulled up with my car, and all of a sudden it started idling different. It bounces consistently. As if someone was tapping the gas pedal every second or so.
I could get a sound/video clip of it idling but I'm not sure where to host the file.

Could someone help me out?
I'm not all that car savvy.
Possible vaccum leak?
If so how would I go about finding it?

By the way the guy who was interested in my car understandably lowballed me. I denied the offer.
I've recently got a new job so I've decided to keep the car.

Thanks in advance