XP:

some smoke is normal from machining oil burning off, but if you have copious blue smoke you have oil getting into the combustion chambers. While smoke (or blue smoke slowly trailing down to nothing) can be crud in the cat -- it will burn off when you get it up to temp, but it may have failed. If so, the O2 sensor is also fried.

If the smoke is black, look for a bad coolant temp sensor or a broken wire/unplugged sensor.

You can check the O2 sensor with a volt/ohm meter -- it should produce 0 volts very lean and about 1 V full rich -- if you have black smoke rolling out the back and 0 V on the O2 sensor, it's toast.

If you didn't have black smoke before, check for a dead temp senor or a disconnected or broken wire on the temp sensors first.

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!