Poor fuel consumption

[Imr4n]

On my 2001 C180 i am getting 20mpg in mixed driving which equates to about 30miles to £10.

The car was serviced yesterday where the oil, air filter, fuel filter and spark plugs were changed.

The car has not been drivin since so i cant say if its improved. Im guessing it might be slightly improved but i cant see it going to 30mpg which it should be at.

What can be wrong?

 

[Bobby Dazzler]

Do you do much stop/start driving, when the engine is cold?

Leaving home 30 minutes earlier enables me to miss traffic, and improves economy to the tune of more than 30%

 

[Imr4n]

Abit of stop/start driving but mainly a mixture.

Are MAF's are common problem? I know Audi/VW have alot of MAF failures that can cause high MPG. Is this common on a w203?

 

[Bobby Dazzler]

MAF are a common problem full stop as they're fairly sensitive and fragile.

Apparently the part supplied by MB is a Bosch item (at least for some models) and even has a Bosch parts number on it. They can be purchased more cheaper from a Bosch supplier.

 

[Imr4n]

Is there anyway to test it? I was told that i can clean it with electrical contact cleaner and see if it makes any difference?

 

[Bobby Dazzler]

Yes it can be disconnected I believe. Try a forum search to find out more.

Whilst I'm aware it's a likely suspect for all sorts of problems it's not something I have experience of on MBs as my cars don't have one.

I did have an Astra Coupe Turbo, and several people in the owners club always carried a spare as they'd last a matter of months, and it was only a matter of time before they'd use it.

 

[Imr4n]

I took of the MAF and cleaned it today but it has not made any difference to performance or MPG. What else can be wrong?

 

[Dieselman]

Have an emissions test performed. If that's Ok and the engine is running properly then the mixture is Ok.
It could be worth checking the AT level.
Check for things like tyre pressures, binding brakes and dead bodies in the boot.

 

[Imr4n]

Sorry whats AT level?

Its just had new tyres and pads all round. I think ill get an emmisions test done from my local MOT station first.

 

[BlackC55]

When was the last MOT?

Has it got worse?

AT= auto transmission

 

[Dieselman]

New tyres will use more fuel and it might be worth checking the brakes aren't binding after the new pads. They could be tight in the holders.

Go for a drive on a long flat dual carriageway and pull up without using the brakes much, then feel the wheels for uneven temperature.

 

[c240yaz]

Binding brakes are highly unlikely. If they were binding that heavily to cause an increase in fuel consumption, the wheels would be on fire and the pads would be screaming.

It's got to be as suggested earlier, MAF or MAS or other engine problem

 

[Dragon]

Jack up all 4 wheels one at a time and see if it free wheeling?

If you get only 20mpg, it definitely not right, you should get around 30-35mpg unless you live in Picadilliy Circus start and stop or drive only 5 miles a day or an automatic, that right, nothing wrong.

 

[grober]

Other possibility is a faulty thermostat leading to poor engine warm up. The other sensor that affects mixture control is the lambda sensor/s Usually this would throw up a fault code tho if it was way out of spec.

 

[Dieselman]

Binding brakes are highly unlikely. If they were binding that heavily to cause an increase in fuel consumption, the wheels would be on fire and the pads would be screaming.

Do we know they aren't.?
One piece of information the O-p gave is that the car has had new tyres and pads. Worth checking I would have thought as that constitutes a change.

 

[Imr4n]

Thanks for the help guys, is there a Merc specialist in the manchester area who can connect it to a diagnostic machine so they can find out for sure what the problem is?

 

[nickcc101]

20mpg is all i get on local trips and between 25 to 29 on motorway driving. I assume that your C180 is non turbo 2 litre like mine, these are known to suffer from poor fuel consumption.

 

[c240yaz]

Do we know they aren't.?
One piece of information the O-p gave is that the car has had new tyres and pads. Worth checking I would have thought as that constitutes a change.

I'll send one of my airport crash tenders over to stand buy as a precaution

 

[taylor192]

What engine is the C180?

I know the M271 and M111 both suffer from the infamous "leaky cam sensor" that causes the O2 sensor to get fouled.

If you're getting poor gas mileage I'd start with O2 sensors and see what the reading is, a good OBD data logger should be able to tell you if they are operating outside of normal range, yet not enough to trigger a CEL.

 

[daveuj]

Hi have a look at your temp gauge if not 80ish may be themostat MPG will be bad if engine is running cold as i only go 5 miles to work 24/26 mpg in winter & 29/31 in the summer (but can get it down with a bit right foot)
have a 180K so it may be a little better then your 180.
have been using the A38 adds 1 mile (now 6 miles)to journey but gets warm faster so does more mpg (stay at 60/70 max)needs must in this time of high fuel prices.
18" 8j front 18" 9j back 225 x40 + 255x35 have had to learn to drive with a very light right foot.