E220 over fueling

[RavzSa]

Hi All,

Took the car out for a drive this weekend after a few months and noticed that the car is burning rich. I can distinctly smell a strong petrol smell from the exhaust.

From what I understand the ECU controls all of the fueling with info from the MAF. Fuel consumption was also pretty high.

I checked for error codes and didn't pick up any.

Could the MAF be faulty without reporting an error and could there be any other item that could cause this?

Thanks
R

[Bartman4800]

Try some injector cleaner first, poor atomization leads to black smoke.

Can you send some pictures under the bonnet? Earlier W124 had CIS, but yours might have multi point injection...

Bart

[RavzSa]

Hi,

Thanks, I shall try the injector cleaner.

Do you think theres any benefit in using a MAF cleaner as well?

Photos of engine bay below

20221115_183313-1.jpg

20221115_183255-1.jpg

[Bartman4800]

Yes, the MAF sensor is situated just behind the air filter box. Buy some sensor cleaner; if it does not help, there's nothing lost

[John Green]

I checked for error codes and didn't pick up any.

The early HFM system didn't have a lot of error codes that were helpful. One of the first things I would check is that the engine is getting up to operating temperature quickly (87deg) and that the coolant temp sender for the HFM module is reading correctly. Either being wrong will make the HFM module think the engine is cold and keep the mixture rich. Kind of like the coke being on when it shouldn't be.

[RavzSa]

I checked for error codes and didn't pick up any.

The early HFM system didn't have a lot of error codes that were helpful. One of the first things I would check is that the engine is getting up to operating temperature quickly (87deg) and that the coolant temp sender for the HFM module is reading correctly. Either being wrong will make the HFM module think the engine is cold and keep the mixture rich. Kind of like the coke being on when it shouldn't be.

Would you know which is the coolant sensor for the HFM, i changed to single / double pole sensor but was told there is another sensor?

[RavzSa]

Also, the cold start idle / choke, stopped working years ago... not sure if this is linked to this sensor

Even after rebuilding the throttle body it didnt work again

[John Green]

Would you know which is the coolant sensor for the HFM, i changed to single / double pole sensor but was told there is another sensor?

As in you changed from a single to a double pole? If you didn't replace like for like, I would suggest that is the first thing you should correct. Sensors can be quite fussy and need to be the same and either genuine or OE quality.

[RavzSa]

I replaced all 3 coolant sensors this weekend with OE (Topran) - like for like

Didn't seem to make a difference but at least Iis all new now