One thing to check is whether the idle valves are working.

You will see two conncectors at the base of the carb. With the igition off, loosen the connectors so you can pull them off easily, but leave them attached. Turn the ignition on, and unplug and re-plug each connector. Each time you do this, you should hear a "click." If you don't, then the valve is bad and needs to be replaced.

These valves are open when the ignition is on, closed when off. Their function is to stop fumes from escaping when the engine is off. If they don't open, the idle circuit does not get any gas.

The problem you are facing is that these carbs did not work very well even when they were new, and they are very difficult to repair as they age. They develop vacuum leaks from heat and over-tightenting and wear around the shaft bushings. With a 1976 car, you have the latest and best of the 4A1's but it is also in the middle of the most complicated emissions system, which has all sorts of pieces that can cause problems. You could well have a switch or relay failing causing the hot idle problem.

If you are going to try to troubleshoot, get a copy of the "Service Manual Engine M110" from Mercedes or eBay, which has great detail about the carb and its surrounding systems.

__________________
Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe