If you had a bad head gasket, you will need to replace the O2 sensor. I don't think they like glycol and I know then don't like burning oil.....

Next, you need to measure the duty cycle at the diagnostic connector (I think it's the round one with a screw cover on the fender like the one on the W124, but someone will correct me if I'm wrong). I think duty cycle should be 50% at idle, engine warm, but flucuating. If it's steady, you have a problem.

You have to measure CURRENT at the EHA, not voltage. Should be 8 mA in normal operation, drop to 0 for full lean (fuel shutoff on coast) and go to 16mA full rich.

If it runs fine until its warm, chances are the fuel distributor is fine, although it's possible it's been monkied with (I hate hammer mechanics!). Replace the oxygen sensor and re-set the fuel mixture properly before getting too excited -- it's entirely possible someone messed around with the mixture to cure the "rough idle" from the bad head gasket!

Peter

__________________
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!