Mercedes-Benz E420 Spark Plug Replacement at your home or office.

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Spark Plug Replacement Service

How much does a Spark Plug Replacement cost?

On average, the cost for a Mercedes-Benz E420 Spark Plug Replacement is $144 with $49 for parts and $95 for labor. Prices may vary depending on your location.

CarServiceEstimateShop/Dealer Price
1994 Mercedes-Benz E420V8-4.2LService typeSpark Plug ReplacementEstimate$213.55Shop/Dealer Price$255.69 - $342.74
1997 Mercedes-Benz E420V8-4.2LService typeSpark Plug ReplacementEstimate$474.02Shop/Dealer Price$581.34 - $832.29
1995 Mercedes-Benz E420V8-4.2LService typeSpark Plug ReplacementEstimate$193.55Shop/Dealer Price$235.72 - $322.79
Show example Mercedes-Benz E420 Spark Plug Replacement prices

What are spark plugs and how do they work?

Spark plugs are one of the key components of your vehicle’s ignition system. They ignite gasoline and air inside of your engine. This gives your engine the power to propel you down the road. The spark plug takes high voltage electricity from the ignition coil and creates a spark at just right moment during the engine’s combustion cycle. This gives the engine the best mix of power, fuel economy and low emissions. However, the electrode at the end of the spark plug eventually wears out and can cause performance issues.

Spark plugs-MATROX-1

When should you replace spark plugs?

Replacement should follow the vehicle maintenance schedule. This will be listed in the vehicle’s owner’s manual. Some cars require regular replacement at 30k, 60k or 100k miles. It is possible in some cases that a spark plug might fail before the service schedule, but it’s not typically common.

Avoiding spark plug replacement can cause:

  • Difficulty starting your car.
  • Check engine light for a misfire code.
  • Flashing check engine light during acceleration for misfire, this can cause engine damage.
  • Reduced fuel economy and/or power.
  • Rough idle and/or unexplained engine vibration.
  • Failed State emission testing.

Even if only one spark plug is found to be faulty, they should always be replaced in sets. Most engines will require 4,6, or 8 spark plugs.

How do mechanics replace spark plugs?

Spark plugs are threaded into the engine’s cylinder head(s). Most cars have one plug per cylinder, so a four-cylinder engine will have four plugs, a six-cylinder engine will have six plugs, and so forth. The mechanic will:

  • Have the correct spark plugs on hand for your vehicle
  • Pull any diagnostic trouble codes that may be related to worn spark plugs.
  • Remove the original spark plugs and look at removed spark plugs for any clues indicating engine mis-operation exists; such as oil burning, excessively rich mixture, pre-ignition damage etc. Inform owner of any found unusual conditions.
  • Install new plugs using a torque wrench.
  • Finally, a road test of the vehicle to confirm normal operation.

Is it safe to drive with worn spark plugs?

Yes, but spark plugs that are worn enough to cause engine-misfiring have the potential to cause engine damage and overheating of the catalytic converter. Regardless of the age of the plugs, or mileage, if the engine misfires or runs poorly, the plugs should be inspected for defects. Generally, spark plug failure will not keep the engine from running, but in cases of extreme wear, you may experience a limitation in the speed at which you can drive the car. If the maintenance schedule says the plugs should be replaced, it is best to do so promptly.

When having spark plugs replaced keep in mind:

  • High-speed driving may accelerate spark plug wear. Consider earlier than required inspection and tune-up if you operate the car in severe conditions.
  • Plugs should always be promptly replaced per the manufacturer maintenance schedule even if they appear to be working perfectly.
  • If your vehicle is equipped with spark plug wires (as opposed to a coil-on-plug system), the wires should be replaced at the same time. This may increase the cost of your repair.
  • It is possible that when doing a spark plug replacement, your vehicle may also need additional parts like ignition coils, this will add to the repair cost.
  • Some engines require that the intake manifold be removed while replacing spark plugs. This may increase the parts and labor cost for the repair.
  • Leaking valve cover gaskets, which have let oil get in contact with the spark plugs, coils or wires, may be the cause of ignition system issues. Valve cover gaskets will need to be replaced in addition to the spark plugs, wires or coils. This will add to the repair cost.

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Meet some of our expert Mercedes-Benz mechanics

Real customer reviews from Mercedes-Benz owners like you.

Excellent Rating

(24)

Rating Summary
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Kahlin

17 years of experience
41 reviews
Kahlin
17 years of experience
Mercedes-Benz E420 V8-4.2L - Car is not starting - Chula Vista, California
Kahlin is a real cool guy, great attitude, arrive on time, and did his best, sadly he wasn't able to give me a diagnosis so it was a waste of everybody's time.

Chris

11 years of experience
82 reviews
Chris
11 years of experience
Mercedes-Benz E420 V8-4.2L - Window Regulator Replacement (Driver Side Front) - Keyport, New Jersey
Very good service at a fraction of the price other places were charging. Will definitely be using again in the future and recommending to others.

Ben

41 years of experience
1410 reviews
Ben
41 years of experience
Mercedes-Benz E420 V8-4.2L - Water Pump - Houston, Texas
Courteous, knowledgeable, and kept in touch each step of the way. The wrong part was ordered and Ben handled things like a champ. I would certainly have no problems recommending.

Tien

23 years of experience
903 reviews
Tien
23 years of experience
Mercedes-Benz E420 V8-4.2L - Transmission Fluid Service - Berkeley, California
Prompt and competent.

Excellent Rating

(24)

Rating Summary
18
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Number of Mercedes-Benz E420 services completed
264+
services done by our mechanics
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