My Jetta Mk4 TDI engine is hard to start in the mornings when the temperature is down around 16° F. When you turn on the key it goes like it's going to start, but the idle remains down. I continue starting for even up to half an hour eventually idle goes up and start.
I don't know what exactly could be the problem. I have been asked to put new glow plugs, new battery, and also service the starter. All this I have done. Still the problem remains. I need some ideas. Please help me sort this problem.