Loss of mpg and running rough-ish 220cdi w211 2008

[Jonny Moore]

For nearly a year now I've had a problem with this car running rough and the next day driving like a dream. When it's having a bad day it will sound more rattly and going through the gears is an effort, on a good day it will simply glide down the road and is a pleasure to drive.

Over the last week or two it has seen far more bad days than good, and i've noticed a considerable drop in fuel consumption. I do at least 1000 miles pw and where it used to return around 45 on average I'm down to 35.

I've thought for a while that it had an injector issue but when put on Star a few months back there were no issues found.

The egr is clean and working freely.
Not sure if it's related or not but when running poorly the car will want to be in higher gears, when driving steadily in traffic at 25mph for instance it will be running at 1100rpm, which obviously sounds bad and makes the car shake.

Any ideas before Star (Caversham) see it next week ?

 

[television]

There are a few things on a diesel like flaps and things, but the MAF could cause it and often OK sometimes and not others

 

[alexanderfoti]

The fuel consumption could be a bit of a red herring.

Its been very cold over the last couple of weeks and I find this REALLY impacts mpg on my 320cdi.

How is your idle in neutral?

 

[Xtractorfan]

Have you tried some injector cleaner, certainly wouldnt do any harm and around a fiver a bottle

 

[Jonny Moore]

Idle is solid, and I use a bottle of Redex every 4 or 5 tanks....

 

[Steve@Avantgarde]

I have a C220CDI. Last week my Mrs parked over a high kerb, when she reversed off it flexed the bumper and cracked the intercooler (the amount of times I have told her not to do this is now by the by, but I digress) since then the economy has dropped 8mpg and the idle speed is all over the place, I drove it over the weekend and didnt notice a huge difference in performance but I can hear a hiss from the front when I rev it up.

Im fitting a new intercooler next week when I expect all to be well again.