Merc drinking like a fish

[flooritforever]

Hi all. I would appreciate your help with my motor! I have a 1999 Merc C200 that has recently developed a serious drinking problem. I'm barely getting half the mpg I was. Can anybody give me any suggestions as to possible causes? The car is driving fine mostly, but occasionally it will stall when i'm coming to a stop at a junction, although it restarts immediately without problem, or have a lumpy idle which can be corrected with a prod of the throttle. Any help greatly appreciated!

[Slinky]

I'd guess @ a Lambda sensor failure..

[flooritforever]

Thats normally located in the exhaust manifold isn't it? Is it an easy repair? Are they expensive? I might also have a small blow on the exhaust, could that have an effect on fuel economy?

[Huff]

yes it could: if the blow is before the lambda sensor, and sucks in air, the ECU will try to richen the mix to maintain F:A at the sensor = worse MPG.

But for consumption to be as badly affected as you say - duff sensor and ECU going into 'limp home' mode is probably a good guess. New sesnors aren't very expensive.

[flooritforever]

The possible blow is halfway down the exhaust, so i think we can discount that. Right, new Lambda sensor it is! Thanks for the help guys!

[flooritforever]

Update!!

I am SUCH a numpty!

After filling up the other day, not to long after posting this topic, I spotted the nearby air/water machine was free, and promptly toddled over to check the tyre pressures.

To my utter horror, I discovered that all my tyres were down to almost half the pressure they should have been at . Despite this, they didn't appear to be down at all!

Pumped them up to correct pressures, and as if by magic, the fuel economy of the merc improved enormously!

Haven't bothered with a new Lambda sensor. Must check tyres every week from now on......

[Slinky]

[flooritforever]

Slinky said:

indeed!