I've just purchased a 2000 S40. When I run the A/C the engine will surge, especially when idling. When idling without the A/C on the engine stays at around 500 rpm. When the A/C is running, however, the engine will surge to around 1200-1500 rpm. I haven't used the A/C while driving since the first time this happened. I have seen in various places online that this may have something to do with the throttle body or ETC(?) needing to be cleaned. If so, is this practical to do myself, or should I find a mechanic?

Additional details:

The CEL is on, reading comes back that the catalytic converter needs replacing (I'm new to Volvo so I don't know if this could be related or not)

Any advice would be great!
Thanks!

 

The Check Engine for the cat convertor is quite common. It's the lower O2 sensor needing replacement mostly. Places like Advance and Autozone sell OEM style replacements. You can get the generic cut-n-splice O2 sensor if needed to save some cash. (The OEM type is much easier to use)

The 2000-2004 1.9L engines have throttle bodies. The newer 2004.5+ engines use the ETC. Cleaning is pretty easy with throttle body cleaner after removing the intake tube. Open the butterfly and spray it inside well. There is usually allot of junk built up in there after a long while with no cleaning. Sea Foam is another product for cleaning the intake although it takes a bit more work to use properly.

While you are cleaning out the TB take a look around the front of the engine to make sure all your hoses are intact. There is a 1" diameter hose up front that gets brittle and breaks that can cause idle issues.