I think you're dealing with an ignition problem. Have you ever replaced the wires, rotor and distributor cap? If not, those parts are now old enough to warrant replacement. If there is no oil fouling on the plugs, then it's not likely that rings are the main problem. You might consider getting the engine 'scoped by a tech who knows what he's doing. But, if the ignition parts mentioned are original, I'd get some new stuff and see if that helps. It sure won't hurt..
1987 BMW 325
[This message has been edited by jeffsr (edited 04-23-2000).]