W204 Cold Idle Issues

[Priceless]

Hi There, Firstly allow me to apologise for asking a question on the day I joined the forum, I came across the page whilst searching for a solution to my idle problems.
C220 CDi W204 auto, really stunning car but yesterday I started her up, and tried to reverse out of the garage, and she cut out, started Okay again and I noticed she is hunting, about 300rpm fluctuation on idle.
Once warm it almost goes away, the fluctuation is not apparent unless you are looking for it.

Has this been discussed on the forum before ? I tried searching but nothing that matches my symptoms is apparent.
Please could someone point me in the right direction of where to possibly find a case which has been solved, or possibly offer up some ideas of what it could potentially be ?

Many Thanks

 

[Priceless]

Further to the info I supplied above, about 4 months ago the car was overfueling heavily - smoking & shocking consumption figures, the intercooler and associated pipes etc were replaced under warranty by MB and all was resolved. I was thinking, maybe the soot etc which was forced through the system during this time has now caused issues with the o2 sensors ?
No Engine Management light is illuminated and my OBD code reader is not picking up any faults, so im not sure this is the issue - anyone got any thoughts on this ?
Car is out of warranty now unfortunately...

Thanks

 

[geraldrobins]

Further to the info I supplied above, about 4 months ago the car was overfueling heavily - smoking & shocking consumption figures, the intercooler and associated pipes etc were replaced under warranty by MB and all was resolved. I was thinking, maybe the soot etc which was forced through the system during this time has now caused issues with the o2 sensors ?
No Engine Management light is illuminated and my OBD code reader is not picking up any faults, so im not sure this is the issue - anyone got any thoughts on this ?
Car is out of warranty now unfortunately...

Thanks

Go back to MB. Their repairs usually have a 2 year warranty. And suggest or argue that this problem is associated with the original problem.

 

[Priceless]

W204 Idle issues - with video

Update to my issue, as suggested I took the car to MB, they had it for two days, returned it without any resolution, there are no codes and the car performed perfectly in the time it was there.
I take it home, everything is good for 3 days, today however the gremlin returns, in London traffic, prolific idle surge and cutting out. Once out of the traffic and up to motorway speeds its absolutely perfect.
When I got home I made a short video which is here https://youtu.be/6dI3vyOYODU
It is strangely enough worse if the gearbox setting is in C as opposed to S or M

All filters are new, including air and fuel.
EGR valve is clean
cant see any obvious vacuum leaks

Please could someone offer some advice/suggestion or failing that, let me know where I can find a specialist independent in the Buckinghamshire vicinity.
Many Thanks

 

[Yugguy]

Autoclass in MK have a good rep.

 

[Priceless]

Thanks, I will make a turn past there as soon as possible, hopefully they can help quickly - given the time of year !
Thanks for your response

 

[Priceless]

Morning All, just got back from Autoclass, MB specialists in Milton Keynes, quite an impressive looking setup.
Anyhow, a chap has a look and says its either the injectors or the fuel pump, but then he says if its the fuel pump they will have to drop the Engine to replace it.
I have just done some checking on the internet and the only location I can find for a for the pump on the w204 is under the rear seat, can anyone confirm this for me please ?

They ( Autoclass) are booked up until end of January, so I need to look for alternative garages who can help me asap.
Thanks.

 

[4life211]

Morning All, just got back from Autoclass, MB specialists in Milton Keynes, quite an impressive looking setup.
Anyhow, a chap has a look and says its either the injectors or the fuel pump, but then he says if its the fuel pump they will have to drop the Engine to replace it.
I have just done some checking on the internet and the only location I can find for a for the pump on the w204 is under the rear seat, can anyone confirm this for me please ?

They ( Autoclass) are booked up until end of January, so I need to look for alternative garages who can help me asap.
Thanks.

it has 2 pump.A little electric pump is located under the rear seat and the big one the high pressure is located in engine

 

[grober]

Off the top of my head without the benefit of any measurement figures ---- I take it the MB specialist put it on Star to obtain live engine data?? ---- I would suggest a partially blocked exhaust?

 

[Priceless]

I have booked the car in, mid Jan is the earliest they can help me now, I will ask them to obtain some live engine data before pulling the engine out to replace the fuel pump.
Thanks for the feedback chaps.

I will update as and when the issue is resolved...

 

[Priceless]

Update - Solved.
Apparently there are two fuel pressure control valves, one in the pump & one on the rail.
The one in the pump was faulty which caused irregular fuel pressure, hence the hunting.
Replaced and all is good.
£60 for the part.
£190 labour, which included diagnosis.



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