I was under the impression that the check engine light will illuminate only if a fault code has been tripped that affects smog emissions. At least it works this way on my car, but it is OBD-I.

__________________
Paul S.

2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".

update

checked codes....nothing....
checked adaption value for m.a.s -----1.21

I am told that the engine light should trigger soon as this is not right..

can anybody please confirm if this means mas is bad.

thanks

That adaptation value does not tell you what is causing your lean mixture.

On the W124 HFM-ECM, the adaptation limit is +- 25%. So, at 1.26, the HFM module would store an Adaptation at limit fault code.

The Engine Control Module tries to keep the air/fuel mixture at the optimum level. There are numerous reasons why at times it is unable to do so, eg. Fuel injectors, vacuum leaks, electrical problems, modules etc.

Ignition Analyzer scope can give you an insight into what's going on at each cylinder, also check the adaptation values at different engine speeds. If the adaptation values are worst at idle, you probably have a vacuum problem. If it is a fuel related problem, it will probably get worse at higher engine speeds.

I suggest getting alldatadiy and familiarize yourself with the various systems of your car. Then develop theories. Based on these theories, you can design experiments and checks to collect data. Then use this data to investigate further in the direction you feel the data is pointing you, and it may lead you the cause of the problem. Sometimes thou, you may have to start eliminating various causes, including replacing parts with good known parts to see if that fixes the problem.

Hope that helps.

__________________
Zafar
94 E320 58000 Miles

thank you for your response.

UPDATE.

as can be seen from my posts i had no tell tale signs of problems..ie. check engine light etc.

i had replaced a whole lot of parts and car was "breaking up" under load.

i reversed all parts replaced and only replaced the M.A.S...

the car drives as new ....no problems

LOOKS LIKE THE M.A.S IS THE MAJOR PROBLEM ON THESE CARS...CHECK IT OUT FIRST.

B.T.W: anybody want to buy 3 new coils still in box and set of 3 plug wires AT HALF THE PRICE.....

PAUL YOU WERE RIGHT ON THE MONEY...