'89 740 turbo, 3 sensors under intake mani

One looks like a knock sensor, i guess ones for temp, but what's the
third one?

Car's been getting 10mpg in town. The sensor By the air filter plenum (
radiator sensor ) was disconnected and jumpered ( not any more, it's
plugged in as it should be ). Which temp sensor goes to the computer (
is it called a DME? or ECU? on V's ; my car's a BMW and I know my way
around them) ok )
I can't see any wires to the O2 sensor but that wouldn't cause such a
poor fuel milage would it?
If I race the motor I get black smoke but it smells like oil not fuel
I'm just beginning on this car, since I've found many get 20 odd mpg in
town.
Any comments received with thanks.

 

There are 2 temp senders, the one with flat pins and blue housing is for
the fuel injection. The one with round pins and the black housing is
for the gauge. When an oxygen sensor is not connected, the computer
goes into a default rich program that will certainly lower mileage.

--
Mike F.
Thornhill (near Toronto), Ont.

Replace tt with t (twice!) and remove parentheses to email me directly.
(But I check the newsgroup more often than this email address.)