Mercedes A140

[smartcdi]

Hey, I know this is not Smart Related but my other car is a petrol 1.4 mercedes A class, it is a 2003 model.

I have been concerned that the MPG is a little cr*p.

Today I filled the tank up to the brim and took it on a 50 mile journey not exceeding 60 MPH and keeping the revs around 2000 rpm.

However the MPG was still in the high 20's, over the past few months we have been struggling to get 30mpg and I just assumed it was due to my wife's short journeys but after today I think there must be something wrong with it.

In the past 6 months I have replaced the air filter (with a merc one), replaced the spark plugs with new bosch ones, changed the oil and filter using a mobile 1 0/40 oil.

Could it be a leak or something else?

Thanks in advance.

[TheAlmostInvisibleMan]

From what you've changed already, it could well be a duff/worn/clogged lambda sensor.

Their operation directly affects fuel consumption, and they deteriorate with age.

(metal canned fuel filters do have a tendency to leak too though)

How many miles has it done ?

[smartcdi]

As always thanks for your reply, it has just done 60k, I don't have any records to show that the fuel filter has been changed.

Thanks

[TheAlmostInvisibleMan]

60K

concentrate on a new lambda sensor

[smartcdi]

TAIM you are bloody good at this!

I went on a website this morning regarding lamda sensors and a sympton of a bad one is that when the car idles it revs up and down which is what my car does.

I think I will go and replace it, on the website it also advised that lambda sensors are replaced around every 40k, I personally did not know that these needed to be replaced.

Thanks very much, by the way are you in the motor trade or are cars just a hobby?

[smartcdi]

Just got some prices, how will I know if I have an upstream or a downstream sensor, was looking at going to Euro car parts who sell a bosch sensor that plugs and plays without any modification. For approx £90, mercedes want £158! - surprise surprise!

Cheers.

[TheAlmostInvisibleMan]

You need the upstream one, (the downstream is just to monitor the cat performance on euro3 engines, which yours will be)

Take your time removing the old one with plenty of overnight penetrating fluid (obviously applied when the exhaust is all cold!!)
It'll be a pig to remove most probably, regardless