1999 E46 320i drinking fuel!!

[Bayerische]

Hi Guys,

I have a 1999 E46 320i that is drinking fuel at a fairly impressive rate. It's using about 12-13 litres per 100km. There is no sign of a leak anywhere.

My thoughts are lambda sensor, it is also taking a long time for the engine to get to temperature so I'm thinking that the thermostat is stuck open. Are these two connected (on choke longer) or am I missing something.

Any advice/thoughts on the high fuel consumption greatly appreciated.

Regards,

Nick

[318 iS Cosmos]

How long is it taking to get to normal operating temperature? When it does, switch the blower to max heat and see if the needle moves back towards the blue zone. Also, check the exhaust tips for black deposits as that's a sign of a rich mixture. It sounds like the thermostat is stuck open. I believe a faulty lambda sensor will trigger an engine management / emissions light.

[JohnH]

Hi Nick,

My old 323ci drank like a fish when the thermostat wouldn’t open, and I had the same recently on the m3 when the lambda sensors needed to be changed so I think it could be eitger, or both.

FWIW, I got oem Bosch sensors from Autodoc which were a fraction of the very best Bavarian could do.

John

[Bayerische]

Thanks John and 318is for the feedback.

Yep, it definitely sounds like the thermostat and possibly the lambda sensor.

Conor has weighed in with some advice so I think I'll change the thermostat and the pre cat lambda and take it from there.

I'll post back if there is an improvement. Thanks again

[Bayerische]

double post

[Bayerische]

Just an update to this thread.

New OEM thermostat, water pump and drive belts fitted to the car with a coolant flush. The car is now heating up as it's supposed to, so the thermostat was definitely broken.

I'm going to monitor the fuel consumption now and see if it improves.

[Valdelisbmw]

Hi Nick,

My old 323ci drank like a fish when the thermostat wouldn’t open, and I had the same recently on the m3 when the lambda sensors needed to be changed so I think it could be eitger, or both.

FWIW, I got oem Bosch sensors from Autodoc which were a fraction of the very best Bavarian could do.

John

just to correct , thermostat opens too early or is not closed properly ,so coolant circulates threw radiator not only in engine and didnt get to the temperatures .if thermostat wouldn't open at all, it would start overheating

[Bayerische]

Now that the new thermostat has been fitted, I have had a chance to see what the fuel consumption is like.

The car is now using roughly 10L/100km which is what you would expect for urban driving, so fingers crossed, problem solved.

Thanks for all the advice.