My 190e used to get about 420km before the fuel light came on.

Gradually, fuel mileage became worse over a couple of weeks.

Now, I'm down to 260km per tank with the fuel light on!

Car runs rich and is smoking - especially bad on acceleration.

Also, severe hesitation from stop.

The only thing that is good is that I don't have problems with cold/hot starts - turn key once without pressing accel pedal.Also, the idle is smooth - have never had any idling problems.

I have run the car with the EHA off (so I should be able to mechanically adjust to the correct mixture) but it is no different - still running rich and I lose cold start capabilities with the EHA off.But sometimes (very rarely), I noticed that with the EHA off I can turn the engine over with the 1st key-on w/o accel pedal so there may be a leak.

Leaning the mixture with the EHA off improves the mpg slightly but results in rough idle (like car wants to die).

So it looks like a mechanical problem.

Ignition stuff have been renewed (plugs, cables, filters, etc) and lube job recently done with fully synthetic oil (every 3 months regardless of mileage).

I have done several preliminary checks/tests on the car.

Coolant temp sensor - measures 277 ohms at 83 deg C (within spec).Car is not running cool and cooling system is working satisfactorily.

Pulled cold start valve with engine running and not leaking.Driven car with cold start valve disconnected but no difference.

I did test my EHA current with an analog ammeter.

Key-on = 10mA
Engine on = 0.25mA
Acceleration = Current goes to -0.25mA
Deceleration = From -0.25mA, blips to 50mA and goes back to 0.25mA

Resistance across EHA is 21 ohms at 83 deg C (within spec).
Voltage across EHA connector key-on (disconnected from EHA) = 3.96V

I also took off the connector at the air-flow potentiometer and checked the resistance at the terminals = 1k ohm with the airflow plate at rest.

At pin X11/3 :

Key-on = 30%
Engine on cold/or at 83 deg C = fixed 49.7% duty cycle

The fixed 50% duty cycle reading when warm seems to indicate an O2 sensor problem.

But the problem exists whether the EHA is on or off, so I may have to resolve the open loop mixture before I can connect the EHA and try to get the car into closed loop.

I have some thoughts on the problem :

Does the zero/basic position on the AFM plate affect the adjustment of the mixture - ie, if the zero/basic position is off, would it result in a car running rich even though the mixture has been leaned?

Also, would a faulty fuel pressure regulator result in running rich and can I test it?For instance, I have heard that pulling off the vacuum hose and finding fuel in it would constitute a bad regulator.

The vacuum hose from the regulator is connected to a breather hose T.One end goes to the intake (i think) and the other goes to the valve cover and air filter housing.I am trying to take off the breather hose at the valve cover with difficulty.

What connects the breather hose to the valve cover?Looks like a kind of a check valve of some sort.What is it's function?

I hope that you experts out there (like Steve Brotherton, M.B. DOC and others) can help me out with this issue.

I have been to 2 indie MB shops.

One told me that my fuel distributor "is not so good" without even doing any checking - probably wants to take me for a good, long ride.The other (left the car with the guy to check) told me that my car is running perfectly, good idle, etc.All he did was richen the mixture (i had leaned it) with the EHA on and told me that he had another similar complaint from a customer and it was "normal".

I don't believe it's "normal" coz the difference in fuel mileage is outrageous!The car used to get very good mpg!

I am very interested in checking/testing further but I need help from you guys out there.

Sorry for the long post and thanks in advance to everyone.