Sprinter 416 CDI: Power Loss Troubleshooting

Hello!!

'I'm experiencing a problem with my vehicle... it starts to shake around 120 km/h, which also affects its performance (top speed). I've noticed vibrations in the engine, and consequently, the whole car. Occasionally, it does regain power, but only for a short time. When I maintain a speed like 130 or 140 km/h, it shakes as if the vehicle is being held back. I've also observed that my brakes are getting quite hot, even without heavy braking (almost not at all), and this applies to all four discs. Are there two separate problems here, or is there a connection between them?'

Note: Year of manufacture 2003, 156,000 km. Engine control unit replaced (with new software by Mercedes-Benz), brakes inspected, new master brake cylinder installed, mass airflow sensor checked, turbocharger replaced (VTG defective, as it consistently triggered the limp-home mode after 80,000 km).

Please, I would really appreciate some advice... since no one knows... what it could be...!! Thank you to all of you and to the owner of this website!

@sprinter1:

Unfortunately, I'm not familiar with the details of the MB CDI engine. However, the symptoms you described could indicate a fuel shortage.
I would definitely start by checking the fuel supply, i.e.

- Fuel filter
- Check fuel lines for air bubbles (if the CDI has a transparent hose).
- Check the pre-lift pump for proper function (CDIs should have an electrically powered pump in the tank).
- Also, also check the fuel tank vent as well. If the vent is blocked, a vacuum will build up inside the tank, which the pump has to work against.

Assuming the fuel supply is okay, there are still many other possibilities. I'm ruling out the turbo and mass airflow sensor for now, as those parts have likely already been replaced or checked.
Unfortunately, I don't know how the boost pressure regulation is implemented in the CDI system. Is the variable turbine geometry (VTG) linkage actuated pneumatically or electrically?
Certainly, you should take a closer look at the turbocharger boost control system, as this could be the reason for the lack of power. If the turbocharger isn't building pressure, the fuel injection amount will be reduced. It's possible that the jerking you're experiencing is related to the periodic reduction of the fuel injection amount due to a lack of air.

Perhaps you should first check the points mentioned above. If you still can't find a solution, you might be able to describe your problem in more detail and provide us with some information about your engine (if you know any).

Good luck with debugging!

Regards,
Alex.