Hello,
The car is a 1976 W115 200 gasoline with the Stromberg 175CDT carb. I have a new carb on it and I have checked the ignition system which is working fine.
The symptoms are:
1. Rough idle after running at 40-60 mph, VERY rough idle after running at 70-90 mph. If it is left to idle for 4-5 minutes, it eventually smooths out.
2. Normal idle if it runs around in commuter traffic around 20-30 mph.
It pulls away from a stoplite without any problem, but there is some snatching in the driveline at constant throttle.

I have checked for air leaks, there are none.

I am suspecting the fuel line,fuel pump or the fuel pump drive cam that is on the oil pump. I know that the drive cam wear was an issue on carb engine BMW of the 1980s, but has anyone experienced this on any Mercedes engine?
This has been driving me nuts, anybody here have any ideas or has encountered this before?

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Nachi11744