Engine accelerates poorly / no longer pulls? Our info!

Recently updated on January 27, 2022 at 10:34 am

In the following article we would like to explain what you should pay attention to (what to check) if your car or the engine no longer pulls properly. First: Watch when exactly the problem occurs. It may happen that the engine only after a cold start, or in a certain speed range. Secondly: Go to the workshop to have the fault memory read out. Tell the mechanics when the problems arise. The following lines explain some possible reasons for finding out why your car is no longer accelerating as usual.

Workshop diagnosis

As already mentioned at the beginning, the Fault memory can be read out. In the best case scenario, a short drive with a connected diagnostic tester is made. Another indication of the cause can be an illuminated engine control lamp (MKL).

Is the turbocharger defective?

The exhaust gas turbocharger, often referred to simply as a turbo, is found in almost all motor vehicles that run on petrol or diesel today. The turbocharger ensures that the efficiency of the engine increases noticeably through an increased air supply. Possible reasons why the turbo no longer works and the car accelerates poorly are often:

• Boost pressure hose is leaking / torn
• VGT adjustment stuck/sluggish
• Defective boost pressure sensor/sensor
• Wear within the turbocharger (plain bearings, rotor shaft, increased bearing play, etc.)

Is the mass air flow sensor defective?

The air mass meter (LMF) is a sensor located in the engine compartment. This registers the air sucked in by the engine in order to be able to inject the necessary amount of fuel. The motor control calculates this. If the LMM is defective, incorrect data or no data will be transmitted. As a result, it can happen that the car no longer accelerates properly when driving, so that no damage can occur. The check engine light or the diagnostic device often indicate this error. Sometimes it can be enough to clean the air mass meter. However, if cleaning is unsuccessful, the component must be replaced. However, a refurbished/used LMM can also be used here. Tip: Depending on the vehicle, two LMMs can also be installed.

Are the tax times wrong?

Timing ensures that the engine's valves open and close at the right time. Possible errors in terms of Tax times can be:

• Defective tensioner pulley on the toothed belt
• Error in the assembly of the timing chain or the toothed belt
• the timing chain is stretched

As a result, the engine often runs unevenly and the engine's performance can be restricted. If you suspect you should go to a workshop quickly, otherwise you will engine failure can occur, which results in significantly higher costs than replacing the component.

Is the brakes tight?

Every car that has a disc brake also has a brake caliper installed on it. On the inside of the caliper are the pads, which are pressed against the brake disc by the brake pistons when braking. Corrosion, dirt or too long Downtimes often lead to the brake caliper getting stuck or stiff. An error in the assembly of the brake caliper during the last brake service is also possible. As a result, the brake provides permanent resistance, which means that the car no longer accelerates as usual. However, it is often possible to repair the brake / make it workable. If this is not possible, new brakes must be installed on each axle. Tip: A brake drum (rear axle) can also be stuck and cause identical problems.

Is the lambda probe defective?

The lambda probes are sensors and are required to ensure the optimum air-fuel mixture. These determine the oxygen content of the exhaust gas and forward the results to the engine control unit. The consequence when a lambda probe is defective is that no or incorrect data sent to the engine control unit. The result is poor acceleration or the engine being switched off in emergency mode. The defective lambda probe must be replaced with a new part as soon as possible. Tip: Depending on the vehicle, you can different Lambda sensors must be installed.

Diesel particulate filter clogged?

The soot particle filter filters out soot particles from the exhaust gases. It's in the exhaust tract. It can happen that despite the (automatic) burning off of the filter, this after a mileage of around 120.000 to 180.000 kilometers congested is. Regeneration is often adversely affected when the Differential pressure sensor is defective. The diesel then no longer accelerates well as usual. If it is no longer possible to burn free, the soot particle filter must be removed and burned free manually or replaced.

Is the engine perhaps drawing in secondary air?

In order for fuel combustion to work properly, the amount of air drawn in by the engine must be relayed to the engine control unit. The mixture used by the engine to move the pistons is prepared on this basis. If additional air flows in, there is reduced acceleration or emergency operation. The following causes can be considered for this:

• a vacuum hose is leaking
• the crankcase ventilation is leaking
• a seal is porous/cracked and leaking

Is the high pressure pump defective?

If your vehicle is direct injection, the engine will have one in addition to the fuel pump high pressure pump installed in the tank. If this is defective, it will result in poor acceleration. It is expensive and needs to be replaced. And in this case it usually gets even worse if, for example, tiny chips have been distributed in the system. This often happens when the pump has seized/seized in the tank. This is often associated with a economic total loss, from Components that have come into contact with fuel need to be replaced or at least extremely laboriously cleaned.

Is the throttle valve defective?

The throttle regulates the intake of air for the engine. The throttle valve is located in the intake tract. Only petrol engines have proper throttle valves. Instead, diesel vehicles often have a flap on the intake manifold. You can often recognize defects in the throttle valve when the engine speed drops slowly after you have pressed the accelerator pedal. This often leads to a reduced performance, which results in poorer acceleration. Sometimes just cleaning the throttle valve is enough. In the event of a mechanical defect, however, it must be replaced with a new part.

Other possible causes of a reduction in engine performance:

1. the vacuum system has a leak
2. the intake system is coked (e.g. by oil carbon)
3. the fuel filter is clogged
4. Defective ignition system causes combustion misfires
5. a defect in the ABS or ESP system
6. a defect in the engine control unit
7. the air filter is dirty or installed incorrectly
8. the accelerator pedal sensor is defective

Of course, that wasn't the end of it!

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