Bouncing Idle

My 1999 Vauxhall (Opel) Vectra has recently developed a bouncing idle. This is much worse if the air-conditioning is switched off and with the a/c off settles to a slightly lumpy idle after a couple of minutes. With the a/c on it settles much quicker (about 15 seconds) to a smooth idle.
Are the posted cures, air leaks etc, specific for the cars talked about or are they general?

They are general. Look also to the ignition timing. If things are off it changes the idle. The computer compensates which changes the timing, which alters the idle again. The computer ends up "chasing" itself around in circles. Another thing to check is the idle air control valve.

I swapped my fuel filter on my Taurus fixed the idle issue, also 10% power increase :)

it's a common problem with 2nd or 3rd gen honda accords, in them it's usually the IAC (intake air control?) valve or something. but that's honda so i'm not sure if it would apply to you.

yeah well, honda's also have bouncing idles when the coolant is too low. Weird little cars they are.

so i should probably check my coolant level, it's getting kind of annoying but i'm not willing to pay for the repairs.

Thanks for the advice.
I changed the air filter but that didn't do anything.
I decided to try to clean the idle air control valve. I got instructions from a Vectra site and bought a new gasket and carb cleaner.
When I got all the hoses off, the valve in the pictures wasn't there. What could be the valve isn't bolted on, it's more permanently fixed. So I just cleaned the throttle bore and butterfly. It took about half a roll of kitchen towel before no more dirt came off (the car's done 126,000 miles). After that the problem's gone. It's running smoother, quieter and not bouncing. Although for the first 10 or so miles the idlle was very high. Now it's like new.
Thanks again,
Tim