Puffs of Black smoke on acceleration, car jerky at low revs, soot around exhaust, occasional lapse into limp mode...

[Nickyp]

Hi - I'd be grateful if someone could help me diagnose a problem I am having...
The car has done about 180,000 miles but has run beautifully until recently. When driving slowly with revs between 1000 - 2000 the car is extremely "jerky" - as though there is either not enough - or too much fuel being pumped in. The problem disappears when the revs are higher than 2000 and if I am travelling at speed - however occasionally the car goes into "limp" mode - which is reset if the car is switched off and restarted. The car idles normally. There is no engine warning light. I noticed yesterday that there is a lot of soot around the exhaust pipes - and when stationary and the accelerator is pushed there is a brief puff of black smoke. I have not noticed this smoke before - and I don't think it is blowing out under normal driving conditions. The car has just been serviced - so I assume the air filter was changed. I've read that it could be a dirty EGR valve - but also could be to do with the injectors. Any advice or ideas of what the problem could be would be greatly appreciated.
Sadly, though I love the car - given it's age and mileage I can't afford to throw big money at it - but I can't help feeling that the problem is relatively minor...
Thanks in advance.

 

[mattkh]

...... The car has just been serviced .
Thanks in advance.

Please itemise the things done at the above service.

 

[mioba]

Id be looking at the PCV valve, an overlooked item on most cars and should be a service item also consider the actuator known weak spot on the M and R class,
Done both on mine last year, Actuator was failing and PCV as preventative maintenance. The PCV was a beach to get at simply because its all tight...uh as was the actuator.

Also depends how you define big money, would putting it right be cheaper than replacing the car....

 

[Nickyp]

Thanks for the responses. In answer to your question re service mattkh it was a standard MB "B service" air filter and oil filter changed and fresh oil. Shortly afterwards the orange warning light came on with a dirty dpf - which was cleaned and fixed (no more warning light) - however I had mentioned the stuttering at low revs and occasional limp mode - they thought that the dpf work would fix it - they were wrong. Attached is a pdf of the codes I got yesterday from a scanner - would that indicate where the problem lies? Mioba - would the codes indicate a PCV valve problem? I take your point re big money...
Thanks again.

 

[mioba]

The are all historic codes, PCV and Actuator dont throw codes

 

[Nickyp]

Mioba - were the symptoms of your problem the same as described above? Also not too sure what you mean by the actuator - which exact part would that be? Forgive my ignorance...

 

[mioba]

For the idling issue it was the actuator - as you describe. Its a small black box on the turbo. MB will say you need a new turbo as the actuator is not availalble seperate (nonsense). The Garret Hella actuator is availabale seperate you need to make sure the numbers are the same (evident when you take it off).
The stick and or the plastic worm gear gets worn down. There are companies that also repair,

Google w251 actuator repair and google W251 PCV valve

 

[Nickyp]

Mioba - hugely grateful for this - thanks. Quick question though - did you have the soot on the exhaust pipes and puffs of black smoke?
Thanks again.

 

[mioba]

No puffs of smoke thats why I also allude to the PCV, you could well have 2 issues.

 

[Nickyp]

OK thanks again.

 

[Nickyp]

Mioba - I just had a quick look at the actuator - from my inexpert eye it appears to be functioning (ie the arm moved when starting and a small amount of movement when the accelerator was pushed). And you mentioned that your problem was when the car was idling - I have no problems with the idle (though it appears a little higher than before - around 750 RPM as opposed to the usual 500 ish) - the problem is only when travelling with the RPM between 1000 - 2000 (no problems when rev-ed to those levels when stationary). Also re the PCV valve there are no particular tell tale signs of problems (leaking oil etc) - but surely if it were the problem (and it may well be) wouldn't it produce blue smoke rather than the puff of black smoke and build up of dry soot on the exhaust pipes? Once again thanks for your help.

 

[mioba]

I dont recall mentioning it when the car was idling.
Just because the actuator looks ok doesnt mean it is. Like I said the worm gear inside gets worn. These things are right near a very hot turbo and also the solders inside can crack - and expand when hot.

I changed my PCV as a precautionarty measure. You wont tell if it is duff looking at it as the diphram inside either goes hard or splits - they do a hell pf alot work fur such a simple item. This will let excessive oil gas though leading to black smoke.

I always get a slight puff of black smoke when i give the car a full super welly - not very often just a mere ego booster

 

[Nickyp]

OK Thanks for your help Mioba - I was confused re the idling as you wrote "For the idling issue it was the actuator..." I have already taken your advice and booked it in specifically to look at the points you mentioned - all above my pay grade. Thanks again.

 

[Nickyp]

Sorry - one other thing - the orange warning light came on this afternoon. The scanner came back with:
P0299
Raw code: 0299
ECU: Engine control unit
Status: Confirmed
OBDII: Turbocharger (TC)/supercharger (SC) - low boost

============2==============
1335552
Raw code: 146100
ECU: Engine control unit[Archive (inactive)]
Status: Test failed since last DTC clear

============3==============
1356288
Raw code: 14B200
ECU: Engine control unit[Archive (inactive)]
Status: Test failed since last DTC clear, Test not completed during this operation cycle

============4==============
1366784
Raw code: 14DB00
ECU: Engine control unit[Archive (inactive)]
Status: Test failed since last DTC clear, Test not completed during this operation cycle

============5==============
1194240
Raw code: 123900
ECU: Engine control unit
Status: Pending, Confirmed, Test failed since last DTC clear, Test not completed during this operation cycle, Warning indicator requested

============6==============
1363712
Raw code: 14CF00
ECU: Engine control unit[Archive (inactive)]
Status: Test failed since last DTC clear, Test not completed during this operation cycle

============7==============
1357568
Raw code: 14B700
ECU: Engine control unit[Archive (inactive)]
Status: Test failed since last DTC clear, Test not completed during this operation cycle

 

[Misterdog]

I always get a slight puff of black smoke when i give the car a full super welly

And some say diesels are dirty and environmentally unfriendly.

 

[sausage]

My Range Rover was deeply embarrassing at one point, similar symptoms, and caused by nothing more serious than a split in one of the turbo hoses. £15 on ebay and 5 minutes with a screw driver to take off and fit the old one. Probably not relevant, but could be worth checking to ensure your turbo hoses are secure.

 

[Nickyp]

Thanks Sausage - I hope it is something like that - but I couldn't find a leak - so off to the garage next week...

 

[sausage]

Good luck and do keep us posted.

 

[star]

Second check your boost hose for small split.

 

[Nickyp]

After sharing the fault codes elsewhere - they seem to indicate a problem with the turbo actuator. Debating now whether to order a replacement from Turbovanes and attempt the repair myself. Having a quick look just now I noticed after the removal of the "Y" pipe a pool of oil where it connects to the turbo - which I assume comes from the PCV valve - which I am told probably needs replacing - however it looks like the devil to get at on an R class - has anyone attempted these and got any tips? I'm assuming for the PCV valve the windscreen wipers need to be removed...? Not sure if I'm up to it or not...!