what will a bad MAF do to a E300?
 

I have been working on a new to me 1999 E300, In the search to make the car run correctly I have replaced the K40, fuel shut off valve, crank sensor, all the clear fuel lines, and cleaned the intake. car still shuts off and has to cool down before it will restart, I have noticed that my scanner reads the LOAD_PCT% at 100% when the car stops, if I'm not mistaken the LOAD_PCT% has to do with the MAF and amount of air that is being brought into the engine. would a bad MAF keep the car from running? I have a feeling its something electrical because the car will restart after it has time to sit and cool down. Any and all help is appreciated.

Sounds like maybe your scanner is the cheapo generic OBD2 variety? I'd recommend getting something Mercedes specific to get the detailed error codes you can't see with generic OBD2.

Personally, I use an Autel MD802 and it's great on the w210, can talk to all the car's multitude of computers and gives all the Mercedes specific codes that make troubleshooting so easy.

Yes, I second that. Apparently there are a number of sub codes for "P0200"

P1220 Fuel quantity actuator (Y23/1) (signal to fuel quantity actuator)
P1222 Accelerator Pedal Position Sensor (R25/2)
P1223 Fuel rack position sensor (Y23/1/1) (signal from fuel rack position sensor)
P1611 Engine control Module – internal reference voltage (N3/7)
P1613 Engine control Module – internal check for delayed shutoff (N3/7)
P1614 Engine control Module – microprocessor / fuel calculation (N3/7)
P1617 Engine control Module – EEPROM or incorrectly coded. (N3/7)

Will the autel MD802 read the specific mercedes codes?

Get a wiring diagram of the MAF then hang a scope / meter on the output and watch actual voltage.

From what I recall, at least the flow meter electronics are pretty much the same as 97+ gas motors except yours does not have a intake air temp sensor. Also, be aware that a 12 v source makes the sensor work and a 5 V source from the computer is modified for an output.

You'll also need the Autel brand 38 pin Benz adapter. The MD802 won't work with generic adapters. The Autel Benz adapter has sort of a black black box attached to it.

Its this one: https://www.mile-x.com/autel-ds708-benz38-mercede-benz-connector-ds708/

And the 15 pin cable to attach it: https://www.amazon.com/Autel-LDS708-CABLE-Cable-for-DS708/dp/B00C4KECU8