Erratic MPG

[Taxing Ken]

My W203 220cdi is presenting odd symptoms. It drives OK but once or twice a week on my regular run to work the MPG drops from my normal 45 - 50 down to 30 - 35. Road and driving factors are unchanged and it has now happened enough to iron out any variables such as weather, traffic etc.

The only 'symptom', apart from the MPG fall has been a very slight hesitancy at about 1500 to 1800 rpm on an even throttle.

Additionally about 3 weeks ago I had a slight fuel leak from a fuel line going into the filter - the dealer remedied this in about 20mins by fitting a new line under warranty. The car is 3 years old with 22k on the clock.

Welcome any suggestions please before I go back to the dealer - you know what they are, if it isn’t leaking, hanging off or making a loud noise they say there is nothing wrong.

Ken

 

[duncanh]

Sorry I can't offer any solution, but I have experienced similar symptoms. On mine the drop is less dramatic. I do the same journey every day (120 miles round trip), usually about 50 mpg, occasionally dropping to 40-45 for a day or two, then back to normal. I have also noted the hesitancy at 1500-2000rpm.

I have been thinking that it is probably the MAF (mine has done 129K miles on the original).

If you have to resort to the dealer, I would be grateful if you post their findings/remedy before I but a new MAF.

Thanks

 

[stivesvelo]

Re: MAF

I replaced mine on the offchance that itwould improve things (was told that it was at the edge of the tolerance), can't say that this made a difference as it has gradually improved, but I have a feeling this could be due to the seasons.

Incidentally I was told that the system needs to be recalibrated to the new MAF & that you can't just change them.

Rob