I have a 1985 Ford Escort with 289000 km and a manual transmission. So the problem is as the tittle says, the car jerks forward when the engine is cold. I wonder if this is a problem with the fuel system or ignition. It runs fine when the engine is warm but living Finland with -30 C outside it takes a while for the engine to warm up. Also the car feels very slow. I know it has 1,3l that originally made around 70hp but i can barely make the car go over 100km/h xD. I just got the car cause it was very cheap so I haven't really done anything to it yet.
My guess is fuel related. If it has a carburetor, check the choke function. I once had a 1982 Opel Kadett with 1,2 L engine that had a manual valve for routing intake air from the exhaust manifold for winter driving. It was also common practise to use cardboard or something else to block the grill to restrict cold air back in the days.
Condensation was also a problem sometimes when it froze in the carb or filter. You may experience the same thing.
Check the basics (filter,plugs etc), if that seems to be ok take a look at the choke mechanism. If it is fuel injected, check the cold start valve etc. Haynes probably have a book covering your car.
It may also be running lean, and that will make the engine even more underpowered during winter.
