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.
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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Related Mercedes-Benz 420SEL Questions

See what others are asking about their Mercedes-Benz 420SEL. Get answers from RepairPal's community of auto experts and enthusiasts.
My 420 has stalled on me twice now w/out warning..but it will start right back up and will perform normal..rough idle...
Car cuts off sometimes when idling and it is losing rpm

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 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