Some time has passed since I last did anything about this little annoyance as I have been pretty busy and the car just soldiers on regardless. I have used the timing light to set the idle speed but have had repeated difficulty getting the cambelt cover off due to all three very rusty bolts. When they were eventually free the top cover does not want to come off as it seems to be sticking at the bottom. I have tested the thermostat in the air box firstly using the methods in the Haynes manual and thinking it was broken, but then sticking it over a boiling kettle which did the trick and the flap did open. I looked at the Warm up box thingy and undid the connectors to find that they were corroded and green (see pics part way through cleaning).
After a good clean I started the car for the first time that day and it started perfectly with no hesitation. Unforunately the next morning I started it again and the problem was back
I am still at a loss. It is possible it could be a head gasket problem as there is a lot of white smoke in cold weather. However, there is no cream sludge in the oil which looks fine, and the coolant looks fine too.
I have cleaned the connecter for the thermal timer but this hasn't made any difference
The vacuum advance unit looks like it has seen better days and does seem to have a white powder residue over it. When I pull the vacuum hose off at idle there is no apparent change in engine note at all (unlike I would get with the Beetle). Is this normal and where would you get a replacement?
I have also cleaned the earth connections for the cold start valve. I didn't touch this when I replaced the seals for the injectors. Could this be the cause of the problem if it is leaking?