Volkswagen Repair: 98 cabrio gls, valve cover gasket, intake plenum

Question
I have a cabrio gls 98.  It has 110,000 on it.  Everything runs perfect except when at idle AS SOON as the a/c is TURNED ON it starts to idle rough.  Without the a/c on its rpms are a constant 900-1000.  When the a/c is turned on the rpms rev between 400-800 almost stalling I think. I checked under the hood for anything obvious.  There is an oil leak that appears to be coming from a head gasket.  That is the only thing I noticed.  There is fresh oil coming from the gasket area and from the looks of the oil build up it seems to have been leaking for a few months.  Could this be related to the idle?

Answer
Hi Amber;
Load on the engine increases, and rpm's drop when a/c is on.  It shouldn't be the kind of load you describe though.  I would recommend that the charge in the a/c system be checked right away.  A recharge is indicated, and reasonably cheap.  If it's the a/c compressor...look out!  The compressor is expensive, and if it let's go, it usually affects everything in the a/c system requiring a high pressure flush with nitrogen gas.  The oil is seeping from the valve cover gasket I expect, and is fairly expensive, but can be successfully repaired in about an hour, and a half.  The intake plenum gasket has to be changed at the same time.  Ask that the engine be steam cleaned after, so it can be demonstrated as to the effectiveness of the repair.

Good luck, Amber.  Hope this helps some.