M103 bad when warm

[pull3rb0y]

Hello community,

first of all, sorry for my bad english. I do my best to describe everything as understandable as possible.

I´m driving a 87´ 300CE with the M103 engine. The car is super well maintained, but has a bit of an engine problem. So far, no workshop has been able to solve the problem.

When the engine is cold, it starts perfectly and runs without a problem.
As soon as the car comes up to operating temperature, it has rough hard idle and shakes when accelerating abruptly up to about 1500 rpm. Everything above 1500 rpm runs super smooth up to the limiter. Also the car has a bad warm start after 15-30 min.

Here is what i´ve done so far:
- replaced KE ECU (car had no cold start enrichment - after that it started working again)
- complete ignition system (Bosch plugs and cables, Beru distributor cap and finger)
- ultrasonic cleaning of the injectors with new seals.
- fuel filter and fuel return line

Some how the duty cycle permanently shows 100%. No matter whether with ignition on or with running engine.
I was once told that I should first get the duty cycle right. Then aim for further diagnosis.

Can I measure anything else on the X11 port to check the duty cycle?

Thanks in advance
Julian

 

[optimusprime]

The engine teperature sensor . If faulty it will send the wrong information to the ECU /For instance if engine is cold , this information is sent via the sensor to the ecu, and the fuel mixture is enriched . .But if the sensor as failed it will continue to send the same message all the time , so the ecu will set the fuel mixture to the engine rich all the time .
It can fail the other way also .Resulting in ECU leaning out the mixture = bad cold start, and rough running see next post for location of t / sensor .

 

[optimusprime]

Location

 

[optimusprime]

And food for thought

 

[pull3rb0y]

Thanks a lot. I read often about that temp. sensor but never really considered it to be the problem.

Is there a possibility to measure it? Or just replace it?

 

[Bellow]

Thanks a lot. I read often about that temp. sensor but never really considered it to be the problem.

Is there a possibility to measure it? Or just replace it?

Looking at the photo in post # 3 there's two of them and if the same with the same connectors it should be possible to swap connections and then it would be the gauge on the dash getting the duff signal.

 

[optimusprime]

Not the same one is for the gauge .

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