Volvo 460 Engine problems

Hi I've got a 1992 Volvo 460 GLE injection (B20F) with a couple of engine problems. Firstly oil consumption is really high, from a full sump (max) after about 200 miles it's barely above the min mark. No leaks are apparent (I guess I would notice this loss of oil) and there's no blue smoke from the exhaust at cold. Secondly, its sometimes difficult to start; the engine turns over but it takes a while to fire, but as soon as it has fired it's fine. At other times it starts as soon as the key is flicked and this problem seems to be unrelated to the temp of the engine. Finally the engine pinks a little under load and I thought the knock sensor would advance the ignition timing to prevent this? The car's done ~100K Any ideas gratefully received. Richard C