This one's got me stumped. I bought a spotless white 1996-7 318iS M44from my Brother-in-law for 3 time under market value. I knew of the problem!!
Heres the history:- B-in-law always took the car to BMW for all services. (Accountant type with no hands-on experience and enough money) This means that the car was well looked after. 18 months ago car developed odd smell from exhaust, erratic idling and heavy fuel consumption (5kms/liter). Took the car to BMW. Long story short spent R21 000 on spares and got the car back doing exactly the same thing. BMW Centurion Says nothing wrong. Yeah Right!!! List of things replaced:- ECM; Air Mass meter; Idle Control Valve; Throttle position sensor; Main and Fuel Pump relays.
I got the car and found following problems which I rectified:- Thermostat stuck open and a big air leak on DISA valve.I have tested and found correct the:- Fuel pressure at common rail test point, fuel pressure valve on common rail, injectors for leaks, electronic outputs on ,air flow mass meter, throttle positioning sensor, idle control valve, injectors.
Not sure of the following:- When engine is idling, if I remove the plug from the O2 sensor (before the cat) nothing happens, no rise or fall in idle speed. I also can't find the O2 sensor relay. Have a 789 page service manual for E36 models and where the book says the relay should be (next to Main and Fuel pump relay), it is not!!??? In the book under fuel it mentions that failed O2 sensor can increase fuel usage. This much?
Anyone got any other ideas, I am all ears.