Mercedes: 1991 mb 420sel, fuel pressure regulator, cylinder compression

Question
I recently purchased a 91 MB 420sel, the idle speed presently is at 1200/ should be 750 +or- 50. Were is this adjuster located under the hood, thank You for Your consideration in this matter.

Answer
It takes special knowledge and tools to adjust this.
I suggest you take it to your local MB specialty shop or MB dealer.
Here is a basic list of possible issues:

Battery
Ceramic Fuse
Overload Relay
Altitude Sensor
Cold Start Valve
E.H.A. Valve
Fuel Injector
Fuel Injector Seal
Fuel Pressure Regulator
Idle Control Unit
Idle Control Valve
Oxygen Sensor
Water Temp. Sensor
Alternator
Distributor Cap
Distributor Rotor
Ignition Coil
Ignition Control Unit
Ignition Wire Set
Reference Sensor
Voltage Regulator
Fuel Filter
Fuel Pump
Catalytic Converter

Low cylinder compression = worn out engine
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