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Mercedes-Benz 420SEL Rough Idle

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

What are common reasons my Mercedes-Benz 420SEL has a rough idle?

While there are a variety of reasons your Mercedes-Benz 420SEL 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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Related Mercedes-Benz 420SEL Problems

Find the most common driver-reported problems that are to blame when a Mercedes-Benz 420SEL has a rough idle.
The rubber boot connecting the throttle body to the intake manifold tends to crack. this can cause hard starting, ro...

Mercedes-Benz 420SEL 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
When spark plugs fail, the engine will struggle. The check engine light will come on, and it may appear either solid or flashing. The driver would likely notice one or more of t...Read More