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.
of the time it's
Vacuum Leak
of the time it's
Spark Plugs
of the time it's
Ignition Coil

Get your Mercedes-Benz issue diagnosed by a professional

Find a high quality auto repair shop or dealer near you

Related Mercedes-Benz E420 Questions

See what others are asking about their Mercedes-Benz E420. Get answers from RepairPal's community of auto experts and enthusiasts.
The car idles rough at times and engine may quit. when this happens the check engine light comes on also where is the...

Related Mercedes-Benz E420 Problems

Find the most common driver-reported problems that are to blame when a Mercedes-Benz E420 has a rough idle.
Failed spark plug wires and/or ignition coils can cause intermittent misfires (rough running); the check engine light...
Oil feed tubes break and fall into the crankcase (engine) and the tappet becomes noisy (ticking), resulting in degrad...

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