W124 Eating my petrol

[Steven Stoole]

Hi All, been a while, my w124 E280 with M104 motor seems to be drinking a lot more since i overhauled the motor? It has been a while since i did the motor but have not really used the car much. it has been sitting in my garage.
At present i recon i am getting 400km to a tank. And even though our petrol is not as expensive as yours it still hurts to have to full up so many times in the month now that I'm using it more.
Someone mentioned or read somewhere that you should check for faults and clear them with a blink tester, and this should make a difference?
On these models can you change fuel air mixture or is this governed by the airflow sensor.

Thanks and look forward to the replies
Steven

 

[kth286]

For comparison, my 95 320 coupe 124 will do 400 miles to (standard size)tank.

On 95 octane petrol.

It has same 104 engine but bigger capacity.

Fault codes would be good to get.

Then clear them, and drive car again and read codes and see what comes back. Those will be the currant codes.

Let us know the codes and we can perhaps provide some guidance.

 

[kth286]

Fuel air mixture is automatic.

As well as reading fault codes, it would be useful to connect a vacuum gauge to see state of engine and determination of air leaks etc.

 

[tonyc280]

My 97 C280 does at least 450 miles to the tank.

 

[grober]

dup

 

[grober]

Lots of reasons for increased fuel consumption so difficult to track down.
These cars have a MAF for fine mixture tuning -
Could benefit from a new one?
Could be a inlet manifold leak,
Could be the heater on the lambda sensor is faulty,
Could be a faulty engine coolant temperature gauge meaning the car is running slightly rich [ Does the car appear to run hotter/colder than it used to?]
Could be partially blocked catalytic converter- if it has one?
Could be transmission slippage ,
Could be binding brakes.
Could be a fuel tank/pipes leak [ usually from corrosion]

sorry can't be more help

 

[Steven Stoole]

Shew, thanks for that, time to track this thing down, i will start with the codes and go from there but check for leaks as well. Thanks for the advice guys, much appreciated

Steven

 

[Steven Stoole]

Tell me anyone got the diagram for the blink tester, i found one on the site last week but cant seem to find it.

Thanks

 

[mejermy]

This should do it...........

 

[Steven Stoole]

This should do it...........

sorry but couldn't see anything?

 

[grober]

Here you go

 

[Steven Stoole]

Here you go

many thanks Grober

 

[Steven Stoole]

So I did the blink tester on the car and only came up with one fault 46 which is resonance intake manifold switchover valve. Reset it will drive gone later and re test it.

 

[grober]

IRRC there are one vacuum operated actuators involved to operate the manifold switchover valve ? It operates on vacuum but the vacuum is controlled by electrically operated solenoid valves. The ECU will monitor the electrical operation of the solenoids and show up any faults but will not of course show any vacuum problems.

 

[kth286]

So I did the blink tester on the car and only came up with one fault 46 which is resonance intake manifold switchover valve. Reset it will drive gone later and re test it.

The plug probably has not been put on properly after the overhaul of the engine.

OR wire has been trapped and is shorting to earth.

 

[Steven Stoole]

The plug probably has not been put on properly after the overhaul of the engine. OR wire has been trapped and is shorting to earth.

Check code again and came up when I reached home. So tomorrow will look at the wiring and solenoid. Thanks guys. Would this cause excessive fuel use? Wondering weather I get some isopropyl alcohol to clean maf sensor.

 

[Steven Stoole]

Ok I have fixed that problem and rechecked the codes and all fine. I am looking at replacing the MAF sensor seen a few on eBay but also noticed another sensor on the pipe going to the inlet manifold. Should I replace this as well? There is no catalytic converter on the car.
Thanks guys

 

[grober]

That sensor is an inlet air temperature sensor [ thermistor bead] Will unlikely to be the cause of your increased fuel consumption

 

[hotrodder]

Journey length and driving style makes a huuuge difference... 400km is ~250 miles which is very roughly 20mpg and i've gotten less than that from my (4 speed) 320te when used for shortish trips in heavy traffic. Filling mine from reserve light just come on = about 56 litres/12.5 gallons and used for longish trips on the motorways/fast A roads it'll do around 350 miles/28mpg when not trying to do economy i.e. that's sitting at *cough* mph when conditions allow and not being gentle with it when exiting roundabouts etc. Generally average mid twenties overall

Personally i wouldn't be replacing things on 'the off chance' especially if it's on the origional wiring loom* and whatever you do do not buy a cheapnese MAF off of ebay.

* What year is it? the engine wiring loom insulation on these rot which then can result in all sorts of issues. If yours is one of the affected years and it hasn't been looked at/fixed/replaced then it's doubly pointless replacing sensors as they're only good as the signals they receive/send...

 

[Steven Stoole]

Thanks for this Hotrodder, mine is one of the wiring looms that has been affected. I rebuilt the loom to the coil packs when i overhauled the motor. It is a 1994 model. I was giving it some thought and might as well look at the rest of the loom as well. I just want to get the car as spot on as i can to sell as we are immegrating back to the UK early next year. Here in SA we will get around 2300 pounds for the car. Thanks again