Mercedes Has No Power When Accelerate – Here's Why and How to Fix This

Your Mercedes may lose power because of problems with the fuel pump, a clogged fuel filter, or blockages in the air supply. This issue may also be connected to the turbocharger that stops blowing when you press the gas pedal.

Engine power problems highlights

• Level of urgency:Medium
• DIY inspection:Possible but may be complicated
• DIY repair:Sometimes, possible
• Cost of repair:$200 - $650
• Can you drive?In most cases, yes
• Commonreasons:A largelist of reasons, including fuel and air supply, electronics, glitches, but not limited to those.
• Ways to fix:Use code scanner to locate the problem and solve it

Symptoms of Mercedes losing power when accelerating

First of all, let's figure out if we are on the same page. I will be talking about the situation when your Mercedes drives more or less well but when you want to accelerate and press the gas pedal, it suddenly loses power and accelerates very slowly. The engine may work harshly or even shake, the RPM goes up and down.

After a couple of seconds, the situation may get better and your car will catch up on the speed. But experiencing this annoying symptom is pretty disturbing, especially if you have a relatively fresh German luxury car and it hasn't don't that before.

Although there are about twenty different units and modules that can cause this issue, I've chosen the most common ones to let you know the basics and to start your troubleshooting right when you are reading this article.

What are the reasons for the Mercedes losing power when speeding up?

As I've already said before, I will try to pick up the most common reasons instead of listing them all in this article. I'm pretty sure you will find the solution to your problem below. If not, please contact the dealership or a trusted repair shop for proper diagnosis and repair. Mercedes cars can surprise you with breakdowns and problems that are extremely hard to locate.

So, here are the most common reasons for power loss during acceleration in Mercedes vehicles:

1. Fuel pump failure

Whatever type of engine you have in your Mercedes, it's likely using the two-pump system to create mind-blowing fuel pressure at injectors. While the low-pressure pump that's located in the fuel tank usually lives very long, the HPFP or High-Pressure Fuel Pump is a pain in your neck, not to say it worse.

This unit will certainly last about 100K miles and then it will need replacement or overhauling. One of the most obvious symptoms of a high-pressure pump failing is that the engine works very poorly when you press the gas pedal. At other times, when the fuel pressure is not so high, your Mercedes can be completely OK.

Looking at reports, I can say that replacement is the only reasonable option, in this case. But the HPFP for your Mercedes is not going to be affordable at all.

2. Low fuel pressure because of the fuel filter

Fuel filters need to be changed at least every 20-25 thousand miles. I recommend changing them more often in older cars - every time or at least every other time you change the oil. This will help you avoid clogging the fuel filter.

This is the cheapest repair - you will just need to change the fuel filter and the car is good to go.

Lots of Mercedes owners ask why the filter is clogged. In most cases, it's about the quality of fuel you buy. But sometimes, the problem is in some deposits in the tank that are sent by the low-pressure pump directly to the fuel pump. Maybe, fuel tank cleaning is a good thing to do if this happens with your Mercedes too often.

3. Air intake blockages

So, the main reason why your Mercedes hesitates when accelerating is that something is wrong with the air-fuel mixture. While we've already spoken about fuel issues, there are also air problems that can happen.

First of all, check the air filter and the pipes that connect the air filter box to the throttle body. Any kinds of blockages like debris or clogged filters should be removed.

Also, have a look at the throttle body itself. Nothing should disturb the air from coming directly into the engine. If this happens, your engine will not be as efficient as you want.

4. Turbocharger failure

One more possible reason why your Mercedes loses power when you press the gas pedal is the failure of its turbocharger. The majority of modern Mercedes-Benz engines come equipped with turbochargers. If the engine works at low RPM, the turbo is not activated and the engine may work well. But when you press the pedal, the turbocharger jumps in, and here come the problems.

A failing turbo will not blow enough air into the engine and this will cause issues with power at acceleration. You may also notice other symptoms of a bad turbocharger like strange sounds from under the hood at high RPM and oil consumption.

Turbochargers in all Mercedes cars aren't that hard to repair, so it's not necessary to replace them if something goes wrong. But to repair this unit, find experienced professionals that can diagnose the turbo properly and have access to high-quality parts.

5. Ignition issues and cylinder misfires

If you press on the gas pedal and suddenly feel that your Mercedes loses its power and provides you with poor acceleration, one of the possible culprits could be the ignition system. It's all about spark plugs and ignition coils. Although they are pretty durable in these engines, they are still not eternal.

If a coil or a plug starts malfunctioning, the certain cylinder will not work properly. It means it will misfire and the engine will lose power. Again, you will not feel this much at low RPM and during calm driving because you just don't need a lot of power. But once you want to accelerate, the missing cylinder will become heavily noticeable.

Replacing the failing plug or coil is the only option, in this case. Unfortunately, these parts for your Mercedes will not cost just a little money.

6. Injection problems

The last common problem that will cause your Mercedes to lose power when accelerating is the issue with fuel injection. I've already told you about pump problems and bad filters. But the fuel injection may be interrupted in another unit - the injector itself. Although Mercedes injectors are durable and don't fail too often, this idea is worth checking.

One of the injectors may have been clogged because of poor quality of fuel, a clogged fuel filter, or other issues. Also, any injector may fail just because of its age and mileage. At about 10 years or 100,000 miles, it's quite possible that injectors are not as reliable as when they were new.

Cleaning these injectors is quite possible and this can solve the problem. But if one of the injectors is damaged, only replacing it may help you solve the problem.

Any other issues that cause power loss?

There are over a dozen of different problems that can cause your Mercedes to lose power when accelerating. I decided to clarify just the six most common reasons because they are more or less easy to identify and diagnose. Other culprits are much trickier and harder to find.

But here are just some ideas of what may have happened:

• the Mercedes may have gone into limp mode because of engine or transmission failure;
• there is an issue with one of the throttle sensors and the air-fuel mixture is not correct;
• the catalytic converter is clogged, exhaust gasses have no way to get out of the engine;
• the issue with the EGR may also cause power loss at acceleration;
• the engine is old and has lost its efficiency;
• the transmission isn't working properly at acceleration;
• there is an issue with your AWD - it turns on when not needed.

I can continue with these reasons some of which are pretty common for older Mercedes vehicles. But to locate them, you will most likely need to visit a Mercedes dealership.

One bad news is that the cost of parts and labor at dealerships is ridiculously high. If you have an older car that is not covered by the warranty anymore, you may want to find a reputable and trusted repair shop that is specialized in Mercedes vehicles.

So, now you know what exactly may go wrong with your Mercedes if it suddenly loses power when accelerating. I hope the article helps you locate the issue and repair the vehicle before it affects the comfort and safety of your driving.