How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site. Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask MB Paul Your Own Question
MB Paul
MB Paul, Mercedes Technician
Category: Mercedes
Satisfied Customers: 4317
Experience:  Mercedes Benz Qualified Diagnostic Technician
Type Your Mercedes Question Here...
MB Paul is online now

I have A 160Avantgarde diesel first reg 27/06/2007 now 52000

This answer was rated:

I have A 160Avantgarde diesel first reg 27/06/2007 now 52000 miles serious problem with starting, loses power , does cut ot quite a lot and black smoke - what can I do ??
Have taken to good garage and they have replaced erg valve, air mass meter and some gaskets but still have not soloved this problem.
I look forward to your favoured reply many thanks
Harvey Cooper

Hi Harvey,

The problem could be down to many things and a check for fault codes using a diagnostic tool is required as the first step - do you know if the garage has done this & what faults are stored in the engine ECU?

The EGR system is certainly a common problem on the diesel A Class - however the mixing chamber that the EGR valve locates into is usually very blocked & should be replaced at the same time. Do you know if this was carried out with the repairs?

Turbo faults or injector faults are both other common possibilites - further diagnosis would be required for these.

Also a check of all vacuum lines should be carried out to make sure there are no leaks in the vacuum system.

Let me know if you need anything else

Best regards, Paul

Customer: replied 5 years ago.


yes everything has been on dianostics and still really not showing up with much they now want to dismantle exhaust system there may be excessive back pressure ???

Blocked catalytic converters are not unheard of causing an increase in back pressure - this will usually cause low boost pressure codes to be stored as the turbo cannot get up to the required boost pressure.

Are you sure they replaced the EGR mixing chamber with the EGR valve?

MB Paul and other Mercedes Specialists are ready to help you
Customer: replied 5 years ago.

They cleaned it all out.

I will wait now to have there report when the exhaust isd removed and then see what result will be

Can I come back to you later in the day or tomorow morning.

Many thanks


of course - see if you can find out what faults are being stored

Best regards, Paul

MB Paul and other Mercedes Specialists are ready to help you
Customer: replied 5 years ago.

OK but do you think this would be the answer ??

Hi - blocked cats could certainly be a possibility if there are low boost codes stored.

I would also make sure the vacuum system is free from leaks & the turbo boost pressure regulator is functioning correctly & not sticking.

There are too many possibilities to say for sure at this stage but it is certainly a possible cause IF you are seeing low boost pressure fault codes.

Best regards, Paul