280sl doesn't run smooth under 2500rpm?? Help??

[Betsey1969]

 Its a 1969 280SL 4 Speed, the car loves to be a high rpm but under 2500rpm it stumbles.  Its like a turning on a switch as soon as it hits 2500 RPM its perfect.  Also when the car is cold the idle does not increase, warm or cold its always 800rpm.  I figure there is a problem with my cold start valve but would that affect the car once its warm?  Thanks

[ja17]

Hello,

Start with the simple and inexpensive things first. Probably not the fuel filter but a good item to change anyway. Check or change the ignition points, spark plugs and engine linkage.  The WRD " warm running device" on the injection pump may be stuck in the hot position.  If this were the case the engine would be too lean to run correctly when cold.

What is the history of this car. This can help us do a long distance diagnosis.