Mercedes-Benz S420 Rough Idle

Learn if it's a simple fix or time to seek out a trusted technician.

What are common reasons my Mercedes-Benz S420 has a rough idle?

While there are a variety of reasons your Mercedes-Benz S420 has a rough idle, the most common 3 are a vacuum leak, an issue with the spark plugs, or a problem with the ignition coil.
of the time it's
Vacuum Leak
of the time it's
Spark Plugs
of the time it's
Ignition Coil

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Rough idle and light tapping noise

Related Mercedes-Benz S420 Problems

Find the most common driver-reported problems that are to blame when a Mercedes-Benz S420 has a rough idle.
A faulty mass air flow (maf) sensor can cause erratic/rough engine operation and fuel economy issues. since this sens...

Mercedes-Benz S420 Rough Idle Repair Symptoms

A failing ignition coil will create misfires in the engine, and lead to hesitation, extreme power loss, engine stalling, poor fuel mileage, and illumination of the check engine ...Read More
As we discussed, spark plugs are necessary for any gasoline engine to run. When they fail, the engine is in a constant state of attempting to ignite air and fuel, but cannot. Th...Read More