Engine misfires are one of the most common problems in many Mercedes-Benz cars. Honestly, it is not because MB cars are weak in this area but because most owners forget that spark plugs are worn items that must be replaced at the recommended intervals. As soon as an engine misfire occurs on a Mercedes-Benz, you will notice poor engine performance and strange vibrations that can sometimes be felt even in the driver’s cabin. The first thing that comes to mind when you get an engine misfire is: “This is going to be expensive.” Please take a deep breath because, in most cases, it doesn’t have to be. This article discusses Mercedes Engine Misfire problems, the most common causes that trigger misfires, and how to diagnose an engine misfire on Mercedes-Benz cars.
What does it mean when you have Mercedes Engine Misfire
Under normal operation, the fuel and air mixture entering the combustion chamber of your Mercedes-Benz engine ignites. When the fuel/air mixture doesn’t get ignited, one or more cylinders don’t provide any power to turn the engine, which gets detected by the Engine Control Unit (ECU) and triggers an engine misfire code.
Common Engine Misfire Symptoms
Depending on the type of misfire and what caused it, you will notice one or more of the following misfire symptoms:
- Engine Vibrations
- Loss of power
- Shaking / Vibrations Noticeable at Low RPMS and idle
- Vibrations go away at high RPMS, typically over 3000
- Engine Stalls in some cases
- Poor Engine Performance
- Check Engine Light
- Fuel / Gasoline smell from exhaust
- Blinking Check Engine Light
How to Diagnose Mercedes Misfire Problems
Many mechanics and car owners dislike working on Mercedes because they believe MB cars are difficult to diagnose due to the large sensors and electronics. If you have the proper tools, diagnosing Mercedes cars is easy. Luckily, the misfire codes are stored in the ECU and are very easy (and inexpensive) to retrieve. To diagnose an engine misfire on a Mercedes, all you need is a generic OBD II code reader that can be bought in some cases for under 20 at your local auto parts store or on Amazon’s Best Selling OBD II scanners list. If you would rather invest in an advanced OBD II scanner for Mercedes, then read our article on Top 10 Best Diagnostic Scanners for Mercedes Benz.
Steps to diagnose Mercedes Engine Misfire
1. Turn the ignition to position II. All dash lights should be on. Don’t start the car.
2. Locate the OBD-II port under the dashboard.
3. Plug your OBD II scanner and let it turn on.
4. Hit the Read button to retrieve the fault codes from the ECU. You will get a code such as P0301. These are called diagnostic trouble codes (DTC).
For more help, watch the following video.
What is the Best OBD-II Scanner for Mercedes-Benz vehicles?
The YOUCANIC full system diagnostic scanner is an essential tool for Mercedes-Benz owners and technicians looking to troubleshoot problems with their vehicles. This diagnostic scanner can help diagnose issues with the engine, transmission, brakes, airbag, ABS, steering systems, and more by reading and interpreting fault codes stored in the car’s computer system. With this information, you can make informed decisions about repairs and maintenance, saving time and money.
In addition to diagnosing problems, the YOUCANIC scanner can also reset maintenance reminders and service indicators, ensuring that your vehicle is properly maintained and preventing potential issues from occurring in the future. This feature is especially useful for Mercedes-Benz owners who want to stay on their vehicle’s maintenance schedule without visiting a dealership or a mechanic. Overall, the YOUCANIC full system diagnostic scanner is a valuable tool that can help you keep your Mercedes-Benz running smoothly and reliably for years.
You most likely will get one of the following codes
|P0300 Random/Multiple Cylinder Misfire Detected|
|P0301 Cylinder 1 Misfire Detected|
|P0302 Cylinder 2 Misfire Detected|
|P0303 Cylinder 3 Misfire Detected|
|P0304 Cylinder 4 Misfire Detected|
|P0305 Cylinder 5 Misfire Detected|
|P0306 Cylinder 6 Misfire Detected|
|P0307 Cylinder 7 Misfire Detected|
|P0308 Cylinder 8 Misfire Detected|
|P0309 Cylinder 9 Misfire Detected|
|P0311 Cylinder 11 Misfire Detected|
|P0312 Cylinder 12 Misfire Detected|
- If you are reading fault codes such as P0301 through P0312, that means that, most likely, the problem is with one of the cylinders misfiring. This is due to a bad spark plug, spark plug wire, or ignition coil issue.
- If you are reading a P0301 through P0312 code plus another code, let’s say P0100. Likely, the P0100 fault code, which refers to a malfunction in the mass air flow sensor circuit, is also causing the misfire codes and even a limp home mode. Lime home mode means the transmission gets stuck in gear, typically in second gear.
The bottom line is that you must research all the codes your OBD-II scanner retrieves from the ECU. Now let’s talk about some of the most common reasons that cause engine misfire and check engine light on in a Mercedes-Benz car.
Common Causes of Mercedes Engine Misfire
The #1 cause of Mercedes engine misfires is old spark plugs. Spark plugs don’t last forever. They are wear-and-tear items. Standard copper spark plugs last up to 30k miles, while iridium and platinum spark plugs can last over 60,000 miles. If your Mercedes-Benz has over 80,000 miles and still has the original spark plugs, it makes sense to change them before you pour money on any other repair. New spark plugs will make your engine run smoother, and you will even see an improvement in gas mileage. Remember that Mercedes-Benz V6 and V8 engines utilize two spark plugs per cylinder. That is typical in Mercedes-Benz engines such as M112, M113, M272, and M273 found in E, C, S, CL, CLK, ML, GL, G, R, and SLK Class. For example, if you have an E320 (M112 engine) or an E350 (M272), your car has six cylinders but requires 12 spark plugs.
Replacement spark plugs for your Mercedes-Benz can be purchased on Amazon to save money on parts.
- Check Mercedes Spark Plug Prices on Amazon
- DIY Guide:
If you replaced all the spark plugs but are still getting an engine miss fire code, the next item to check is the ignition coils. Mercedes uses one coil per cylinder. In some cases, each coil may power two spark plugs. Ignition coils are easy to replace, and you don’t necessarily need to replace all of the ignition coils if one has failed. Replacing the ignition coil is very straightforward. You must unplug the coil, remove the bolt, disconnect the spark plug wires, and reinstall in reverse order. If you need a replacement coil, you can get them on Amazon for much less than the dealer.
- Mercedes Ignition Coil Pack Replacement DIY Instructions
Mass Air Flow Sensor
The mass air flow sensor is one of the most critical sensors in a Mercedes-Benz car. It measures the temperature and volume of air entering the engine. This is crucial because if the mass airflow (MAF) sensor is bad or failing, you will have poor fuel economy and performance and may also get misfire problems and other symptoms. Pay close attention to the codes and look for the following codes related to the MAF sensor.
Fault Codes related to MAF sensor
|P0100 Mass or Volume Air Flow Circuit Malfunction|
|P0101 Mass or Volume Air Flow Circuit Range/Performance Problem|
|P0102 Mass or Volume Air Flow Circuit Low Input|
|P0103 Mass or Volume Air Flow Circuit High Input|
|P0104 Mass or Volume Air Flow Circuit Intermittent|
|P0171 System too Lean (Bank 1) ) faulty air mass flow sensor|
|P0411 Secondary Air Injection System Incorrect Flow Detected|
|P2011 check B2/6 (left hot film air flow meter).Implausible|
|P2011 check B2/6 (left hot film air flow meter). The signal voltage is too high.|
|P2011 check B2/6 (left hot film air flow meter). The signal voltage is too low.|
If you do find out that the MAF sensor is defective, don’t panic. It is not an expensive repair if you are willing to get your hands dirty. You can get an aftermarket sensor, but we recommend using the OEM MAF sensor whenever possible.
Spark Plug Wires
When we talk about spark plug wires, you may be thinking spark plug wires are a thing of the past. My Mercedes doesn’t have a distributor. But hold on! Mercedes uses wires between the ignition coil and spark plug on most V6, V8, and V12 engines. You don’t have to worry about spark plug wires if you have an engine that utilizes an ignition coil installed directly on top of the spark plug.
While spark plug wires fail less often, we have seen a few cases where those short spark plug wires were either defective or damaged during improper removal. Remember this, especially if you change the spark plugs in your Mercedes and are still getting an engine misfire.
Fuel pressure can cause engine misfires as well. We haven’t seen too many cases where the fuel pressure was the cause of the misfire. Generally, when Mercedes owners experience fuel-related problems, the fuel pump fails. If that’s the case, your Mercedes won’t even start getting that fixed before you throw parts and money on your Mercedes.
If you suspect fuel-related issues, checking the fuel pressure on a Mercedes is very easy. As shown in this picture, you must connect a fuel pressure gauge to the fuel test port.
The Actron CP7818 Fuel Pressure Tester Kit works very well. The Schrader fitting is required to connect to the MB fuel test port. It allows you to test fuel pressure regulators, weak fuel pumps, and leaking injectors.
Bad Catalytic Converter
A catalytic converter that is clogged and restricting the exhaust gasses from leaving the engine can also trigger multiple cylinder misfires. If your catalytic converter is clogged, you will notice a drastic drop in fuel efficiency and a real struggle getting your Mercedes to accelerate. If the cat is completely clogged, your car won’t even start.
Bad Car Battery
The car battery on your MB is very critical, and if it fails, you can experience a list of electrical malfunctions, including engine misfire in some cases. If you must jump-start your MB regularly, it is time to replace the battery.
Internal Mechanic Issue
Mechanical engine problems can also cause an engine to misfire. A Burnt valve or blown cylinder head gasket can definitively trigger misfire code and symptoms. If a particular cylinder is not generating the required compression, the fuel mixture on that cylinder may never get ignited. You must perform a compression test and pay attention to unusual engine noises.
If your Mercedes-Benz has developed an engine misfire, always scan the codes via the OBD-II port. In most cases, a cylinder misfire is caused due to old spark plugs that need to be replaced. A failed ignition coil or a bad spark plug wires. If none of the above fixes your misfire problem, carefully analyze the fault codes; another problem in the engine may indirectly cause the misfire.
Please use the comments section below to report your engine misfire symptoms. If you have already fixed this problem, let our readers know what the cause and solution were in your case.