I don't believe that one has an O2 sensor -- if it does, it will also have a frequency valve that looks just like a electric fuel injector in the fuel return line after the fuel distributor. O2 sensor will be either in the lower part of the exhaust manifold or under the car in the front pipe.

Loss of power on a grade is much more likely to be fuel system related -- check fuel pump relay, fuel pressures, and replace accumulator and fuel filter.

It is has a carb (four barrel) -- although I think it should be fuel injected, K-Jet, the bowl float is too low, and you have no fuel going into the intake on a slope, rebuild the carb.

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!