Jerks during braking and acceleration in BMW – how to fix it?

BMW driver question

The problem is that when I get to an intersection and almost come to a stop, the car jerks when shifting to slow speed. I have never had such symptoms. In addition, during hard acceleration I have the impression that it also jerks. When I connected the diagnostic computer, it popped up the error “250900 fuel pressure sensor”. I replaced the short circuit to the pole and the sensor with a new one, butthe problem still occurs.

The problem was on a BMW 730d G11, but it may also occur on other models.

BM Cars service response

Jerks when braking

The problems you described are very complex and involve several different vehicle behaviors.

The problem of jerking when stopping occurs most often when automatic transmission problems begin. The moment of stopping the vehicle should be combined with the reduction of the gear and, in the final stage, the disengagement of the drive by the torque clutch.

If there is any delay during these operations, it is often perceived as a jerking, knocking or jumping of the vehicle when stopped, or just after. Such a malfunction usually does not trigger errors regarding the automatic transmission in the diagnostic system. The oil in the 8HP transmissions used in the BMW G11 should be changed every 60,000 kilometers (as recommended by the transmission manufacturer ZF). Significantly overstretching this interval or failing to change it, as well as using non-original oil, can lead to permanent damage to the transmission components responsible for smooth shifting and gear reduction, and the operation of the torque clutch.

Jerking on acceleration

The second problem described as jerking on acceleration can also be related to the operation of the transmission. It is most common in vehicles equipped with xDrive and comes from the VTG box, which transmits drive to the front wheels. Improper operation of this box, used oil or too little oil cause a jerking effect during acceleration, which disappears with gentle or steady driving.

The effect of improper operation of the VTG box also occurs when the vehicle has tires with different tread wear or different tread types on the front and rear axles. A minimal difference in circumference between the front and rear wheels causes permanent damage to the VTG box mechanism, resulting in jerking during acceleration. This type of damage does not generate errors in the diagnostic system for a very long time. The oil in the VTG box should also be changed every 70,000 km.

In addition to the transmission system, the source of jerking during acceleration can also be the engine itself. Improper operation of the fuel and injection system – too low or unstable initial and high fuel pressure, contamination of the fuel system with filings from a worn injection pump, poor operation of the injectors. Any of these elements can cause a temporary lack of torque or ignition drop out and, as a result, jerking of the vehicle.

Suggested order of repair work

To solve the problem you described, we suggest the following order of inspection and diagnostic work to be performed:

1. Complete vehicle diagnostics using the ISTA system
2. Checking the quality and quantity of oil in the automatic transmission
3. Checking the quality and quantity of oil in the VTG box
4. Thorough inspection of the vehicle’s tires
5. Diagnostics of the engine injection system
6. Checking the injectors and injection pump on the test bench

After completing the above work, you will be able to determine the order of repair work to be performed on your vehicle.

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