320d high fuel consumption?

[irfaanlall]

Howsit guys

I have a 2008 e90 320d msport A/T which has the n47d20 engine and as the title states im struggling with high fuel consumption. I admit i do have a heavy foot but i have owned the car for the past 12 years and my driving style has been the same throughout the years. Initally with my heavy foot i used to get around 7.7l/100km then in recent years ive been getting 8.4l/100kms now im getting 10l/100kms. Something is not right as it has increased significantly, however the car still feels strong and has been serviced every 10000kms.

I ve replaced fuel filter, air filter etc but nothing makes a difference. I have noticed the car does show error codes for glow plugs. I have asked my mech about it and he says replacing glow plugs are a waste of money in our climate as they are more for colder climates.

Does Glow plugs have anything to do with fuel flow? could this be the cause of my increasing fuel consumption or is there anything else i need to check?

Thanks in advance.

 

[DRCraig]

Does the car still have the catalytic converter in place?

 

[irfaanlall]

Does the car still have the catalytic converter in place?

Yes it does... the car is still 100% stock and mileage is on 199k kms

 

[irfaanlall]

Wouldnt block cats have more serious symptoms rather than just increased fuel consumption?

 

[Rainier Vermaak]

Wouldnt block cats have more serious symptoms rather than just increased fuel consumption?

Blocked cats are death for diesel engines.

 

[DRCraig]

If you get a sulphur exhaust smell, it is most likely that the cats are blocked. Could also be a blocked egr valve. Best is to do a delete on these items. What errors does the OBD-scanner read?

 

[M3boi]

At that sort of mileage I'd expect a decat to be done already yeah. May as well go ahead and do all the deletes.

 

[PsyCLown]

For interest sake, considering this is a diesel engine with higher mileage and the cat and EGR still active - what are the chances of a lot of carbon and gunk having built up and also contributing towards the higher fuel consumption?

Would a carbon clean make a noticeable difference? I have never done this, so curious as to how effective it can be.

 

[Solo Man]

There is a sensor on the inlet manifold that is easy to get at. One small bolt holds it in place. Remove it and give it a clean with carb cleaner or something similar. Also, on the charge pipe leading to the inlet manifold there is another sensor that one can clean. This one needs a quarter turn i think to the left (anti clockwise) and then a straight pull out. It could also have two plastic clips holding it in place which prevents it from turning/falling out. Clean this as well. Do not worry about the glow plugs, as said, we do not need them here in SA. Remove swirl flaps, egr and cats (you can sell the innards of the cat for good money) and whilst at it, clean the inlet manifold as best you can. All this should bring back the economy you are used to. With the M47 motor the egr thermostat and main thermostat were usually the culprits when high fuel consumption was experienced but on the N47 motor i do not think the egr has a thermostat. At least, I haven't seen one on the egr i have removed on my cars.