[Rev]

Are your plug wires on the right plugs? I make that mistake occasionally and the engine won't idle worth a damn on 6 or 7 cylinders, LOL. Go through the firing order and check that. You did say you havn't changed anything recently, so it's not a likely solution. Just trying to cover all the bases. You can pull the plugs and check that they all look OK. A non firing plug will look all wet and a proper firing one will be dry and tan or grey, but I can't see any reason that it would occur out of the blue. Not much help here but I'm trying to think of things.

Rev