the most likely cause is lean running cold, when the O2 sensor circuit is not working and the engine is running in fixed mixture mode. This can be caused by a fairly large vacuum leak (highly likely by this age, all the rubber and plastic is brittle), a bad EHA, a bad fuel distributor, etc. Even a bad fuel pump relay or tired pump can do this.

Best thing to do is check for vac leaks first -- if you just adjust the mixture, it will have to be done again when it get so bad you have to fix the leak....

From there, you need to determine fuel pressures, etc -- time for a visit to a tech unless you have the proper equipment.

Anything beyond fixing vac leaks or replacing a bad EHA begins to get VERY expensive these days...

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!