1960 190Db Question

[Marcb]

I have a 1960 190Db that doesn't seem to be running properly. At a low idle, the engine isn't "even" and the idle seems a bit erratic. It will go up and down every now and then and it usually is puffing out some blue (unburnt) smoke too. Any thoughts? I wasn't sure if pump timing would cause this?

Thanks.