I replaced my glowplugs and my car still hiccups. I never figured out why, so I have just lived with it. Yes, the valves are adjusted, filters are clean, etc., etc. When it is really cold, below 40 for example, the car may stall. One deep seated fear I have is that there is low compression in one cylinder which keeps it from firing until it warms up a little - hence the hiccup. In any event, the car otherwise runs perfectly, so I don't worry about it.

If you solve the problem, please let me know.

Greg
'84 300D, 166k