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MB Paul
MB Paul, Mercedes Technician
Category: Mercedes
Satisfied Customers: 4317
Experience:  Mercedes Benz Qualified Diagnostic Technician
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E-class 11 years old, diesel. Drives well but when trying to

Customer Question

E-class 11 years old, diesel. Drives well but when trying to accelerate quickly suddenly loses power. Will keeping moving but only accelerates slowly. The only way to regain full power is to stop the car, turn off engine, remove key from ignition. Put key back in and restart. Power then fine. Why?
Submitted: 3 years ago.
Category: Mercedes
Expert:  MB Paul replied 3 years ago.


This could be down to many things & a diagnostic check for fault codes should be the first step but here are some common issues that you can check:

Check the intake hoses from the turbo to the intercooler & the intercooler to the intake manifold - these are prone to splitting & only open up when under boost pressure from the turbo, so check carefully!

Also check the intercooler itself for signs of leakage.

Check the intake manifold - there are inlet ports that can leak, these can be difficult to see as they are located on the underside of the manifold close to the engine block. Large oil leaks from under the manifold are a sign that this is leaking.

The catalytic converters are prone to blocking & can sound like an air leak at times due to the pressure build up in the system from the turbo - inspect around the cat joints for signs of soot being forced out, another tell tale sign of this problem.

EGR can cause problems also if blocked so a check of the EGR system is advisable.

Sensor readings should be checked on a diagnostic tool such as Mercedes STAR diagnosis - the MAF (air mass) sensor can be a particular problem.

All of the above can cause the engine to go into limp mode which shuts the turbo down - the turbo itself can also cause problems but all of the above should be eliminated first.

Best regards, Paul

Customer: replied 3 years ago.

Thanks Paul, will get all of these things checked out. Problem has supposedly been sorted previously! Will see what he says now.,

Expert:  MB Paul replied 3 years ago.

No problem at all - all these things can cause the same symptoms (limp mode) so it is quite possible that another component has caused thesame symptoms before but it could be something different this time around.

Let me know if you need anything else.

Best regards, Paul