400E start problem?

Hi, I just got '92. 400E and I think it takes little too long to crank the engine before it will start up. I also have '95. C280 and it starts right up. On the 400E once when it is up and running, idle is very smooth but when you step firm on gas pedal it dos not respond right away. First the rpms will go down like it will stall and then it takes off. If you accelerate slowly or normal just pass idle and then step on it everything works fine. I am not sure but I am thinking that the hard starting has something to do with the bad throttle response. If someone knows what could be wrong please help. I have a scanning tool for this car but it does not have any codes? Car has 118000 miles

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One of the most common problems with the M119 engine is distributor cap/rotor problems. ALSO EGR systems cause build-up of deposits on the throttle plate, scrubbing/ cleaning helps the "around" idle problems.