C280 1997 starts, idles for a while and then dies. When accelerating it dies also, what is wrong with this car?

sounds like a fuel issue / carb or fuel injection problem.

Check for a vacuum leak. Use a spray carburetor . Spray vacuum lines. Sudden drop in RPMs you found the leak.

Clean the inside of the throttle body as best you can. also the idle air control motor.

The first thing you do is to have the fault codes checked with a scan tool.

check or replace fuel filter for clogging up. if it does clog up, then you will not get enough fuel to engine to run it properly. it will stall at stops, and be very sluggish on takeoff. check fuel pressure if need be. could also be a bad catylist convertor. so check above first. Rent a fuel pressure guage from advance or oreilley's and check fuel pressure if needed. they will tell you the proper fuel pressure for your car.

It sounds like there is a problem with the Idle Air Control (IAC) valve. Its job is to open and let air into the manifold when the throttle is closed at idle. If it does not open, the engine dies at idle. The IAC is mounted on the throttle body. Possibly the valve is clogged or stuck, in which case it could be ok again if it is removed and cleaned. Or it is broken, and needs to be replaced. Or, there is a problem with its electrical connection, that needs to be traced. Good luck, let me know if you have any questions.

idle speed sensor maybe bad. check for codes

First thing I'd check is fuel pressure. 55psi

try cleaning the idle air control valve

CHECK THE IDLE SPEED SENSOR, UNPLUG IT AND SEE IF THE VEHICLE REVS UP A BIT. IF IT DOES, THEN REPLACE IT. ALSO CHECK THE FUEL PUMP RELAY IN THE FUSEBOX. HOPE THIS HELPS. .LET ME KNOW. GOOD LUCK