K-Jetronic Flutter
 

I don't know why but the air metering plate on the K-Jetronic (280CE, 1978) has developed a bad flutter. Engine running poorly, then dying. There's a new WUR, new distributor, vacuum seals are good. But this fluttering is severe. Where do I start? Fuel pressure delivery or vacuum issues??

When fuel pressure is low it will do that.

Is your butterfly all clean ?

Yes -- the butterfly is clean.

The fuel pressure is good from the tank.

Do you mean the secondary circuit pressure --from the WUR -- could be weak??

If you hooked a vacuum gauge to the intake manifold, you would get a similar flutter.

Have you tried to lightly push down / pull up on the plate? This would at least let you know if you are running rich / lean.

What is the history of this car? Were the parts changed in an attempt to fix the roughness?

Have you investigated the tank at all for the problem ,if never replaced after close to 40 yrs of service this maybe a good place to start.You can start by simple replacing the fuel filter ,cut open the old one after draining and soaking with water ,youll see what appears to be red brownish dirt ,rust .The answer is replacing with new ,replacing with a good reusable one ,or , cleaning then coating your original ,the cheapest route but has to be done correctly.I had to complete this procedure from tail to nose on a 190e , fuel system was nasty ,even succesfully had the fuel distibutor cleaned with a sonic cleaner ,she ran great.New plugs , injectors ,PUMP and filter wouldnt do it ,it had to be the tank with rust resisting the flow and it was in this case.After 4 months of weekend driving Im confident this car is reliable .