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Mercedes-Benz E420 Rough Idle

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

What are common reasons my Mercedes-Benz E420 has a rough idle?

While there are a variety of reasons your Mercedes-Benz E420 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.
34%
of the time it's
Vacuum Leak
21%
of the time it's
Spark Plugs
15%
of the time it's
Ignition Coil

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Mercedes-Benz E420 Rough Idle Repair Symptoms

A failing ignition coil can create several symptoms: Check engine light comes on Engine runs poorly or stall Increased emissions Reduced fuel economy Car won’t start I...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