EGR (Exhaust Gas Recirculation) valves were not commonly used in gasoline engines until much later.
Here's why:
* Engine Type: The 420 SEL was powered by a gasoline engine (M117). EGR systems were primarily used in diesel engines for emissions control, and in later gasoline engines to reduce NOx emissions.
* Emission Standards: Emission regulations were less stringent in 1986 compared to later years.
If you are experiencing engine issues, it's crucial to consult with a qualified Mercedes-Benz mechanic to diagnose the problem accurately.
Here are some potential issues that could cause symptoms similar to an EGR valve malfunction:
* Fuel injectors: Clogged or faulty injectors can lead to rough idle, misfires, and poor fuel economy.
* Spark plugs and wires: Worn or damaged spark plugs and wires can cause ignition problems, leading to misfires and engine hesitation.
* Oxygen sensors: Defective oxygen sensors can result in inaccurate fuel-air mixture readings, affecting engine performance.
* Air intake system: Restrictions in the air intake system, such as a clogged air filter or a leak in the intake manifold, can affect air flow and engine performance.
A qualified mechanic can perform a thorough inspection and diagnosis to identify the root cause of the issue and recommend the appropriate repairs.
