My W124 230CE is powerless on high rpm's. Present top speed is about 110 km/h. Think I have checked almost everything. Exhaust system from kat and back is changed. Fuel pump and filters are changed. I have tried a lot of second hand parts: Fuel distributor unit, control unit, potentiometer, lambdasond. I have cleaned the injectors. None of these changes has made any significan diffrence. The kompression and the preignition is ok. I'm out of ideas. I hope you can give me some advice

I would suggest you check a few simple things before throwing parts at it.
1) Accelerator cable: Is it adjusted properly.
2) How's you air filter? Any obstructions in the air intake system?3) Fuel flow/pressure . On spec? Kinked fuel line?
4) Check ignition timing.... and camshaft timing.
5) Catalytic converter clogged?
6) Coil output?
JackD

Thanks for your reply. Points 1 to 5 are checked OK. As to the coil: the resistance is according to spec but I donīt know how to check the output. Thanks for ideas.

Did you check your O2 sensor?
Did you check your EHA current with the test harness from Mercedes?
Did you check your duty cycle reading from the X11 connector?
Do a search on all the above here on this forum.
The 190E 2.3 engine is about 99% similar to your 230CE so do a search and you should find some good tests that you should be able to do on your own. You will understand a lot about yor car

Thanks for further ideas. O2 sensor gives 0,47 V at idle. The output from X11 pin 3 is steady around (AC) 4,7 V, (DC) 2,6V. The value raises only when decelerating. With a voltage on 4,7 V the duty cycle is 65%, and with 2,6 V 80%. I have tried another EHA and the voltage to it is 13,4 V.

While testing I accidentaly disconnected the ECU and the engine kept running like before - how is that possible?

I have finally found a major fault. Discovered that I have two catalytic converters on the manifold. They were both broken so the manifold was plugged. Now I just have one last question. Can I drive my car whithout these cat's or do I have to replace them? I'm thinking that the O2 sensor will be getting wrong information and the exhaust will be to polluted.

Doesn't the O2 go into one of them? What year is your car? Are you really sure you have two? I think you only have one and the other thing is a resonator. The CAT has the heat shield.

It's a -89. The O2 sensor is directly attached to the manifold. The CAT comes later. These two things I meant are positioned before the O2 sensor and the remains of them (large parts of them was stuck just before the O2 sensor) certainly look like small CAT's.

I spooke to an mercedesmechanic and he said that they are "pre-cat's"

my 300ce (93, 3.2L) is pretty sluggish at low RPMs, unless I romp on it hard, but it comes alive above 5000 rpm, sound wonderfull, just hate having to wait so long for power

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1993 300CE Brabus Edition
1999 528i

1992 300E

Ah, that makes sense. Troublesome little things. It wouldnt do harm to get rid of them. The pre cats job is to reduce emmisions during cold start I believe. Just make sure your car is plenty warm when you go for Emmisions.
Getting rid of the pre cat is illegal in the US but people do it and find, hello, horsepower!

Thanks again. Well, reducing emissions during cold start makes a lot of sense. I think that it's illegal to get rid of the pre cat here in Sweden to, but no one but me will ever know.