Hello again ....
By setting the idle speed between 850-900 rpm with the motor warm solved the problem re very high idle rpm (>3000). Thanks
However, when the motor runs warm it sounds and feels as if one cylinder drops out: less power and more vibrations. When the motor is started in cold condition later on, it runs relatively well, i.e. the car accelerates swiftly to 70 mph. - and then the problem starts over again. It may happen that the motor suddenly gets its power back and then again lose it - an on-off symptom.
I am aware of the fact that one symptom may have different causes. Does the weber deliver too little fuel to the engine after running a while, or...? What do you suggest?
Regards Palle