Need help on a fault code and persistant Engine Management light

[JC180]

Hi Guys

I have had the Engine Management light come a number of times since march. As far as I recall this is always the fault code: -

P201D-002 Selfadaptation of mixture formation. The mixture is too lean in part load range. [P0171]

Four weeks ago I had the MAS/MAF replaced apparently...another story.

The car drives as normal and my local indie is mentioning oil on the wiring harness which can damage the MAF saying it's a known problem on the Kompressor engines though he hasn't checked.

I do not really know what to do as they are not being very helpful.

All advice most welcome.

p.s. anyone in the manchester area that can strip my airbox to see if the MAS has been replaced? I'm still not convince. Is it an easy job? If so I'll do it myself.

 

[BlackC55]

The air mass is right on top of the air box.

Have you the red top engine?

 

[BlackC55]

Check in No1 cylinder for water ingress.

Get a cylinder leak check done.

It sounds like you have a valve which is not seating properly.

I think I have told you this stuff before.

 

[JC180]

Thanks Ollie

You havn't told me this before btw, we corresponded via PM's on another matter. I do not have the red top engine (see engine bay below) and I know where the MAS is and it did NOT look new that is why I suspect it has not been changed even rhough I spent £416 getting it done. (warranty paid £315 but still...)

What makes you think it is particularly Cyl 1 and how would I check for water ingress?

Cheers again

 

[BlackC55]

They suffer with water getting into the plug hole and missfiring.Worth a look. Remove the top plastic engine cover and remove the coil on number 1 and have a look down the hole. Water contamination should be obvious.

That engine does not suffer with oil contamination so you can rule that out completely.

Get a cylinder leak check done.

 

[Glenn Smith]

P0171 is the P code you should be looking at, fault will be with an intake or exhaust leak, Airflow sensor, fuel pressure, faulty injector or lambda sensor. Take the car to someone who has the ability to read and interpret the fault codes and do the neccessary test work afterwards.

 

[JC180]

They suffer with water getting into the plug hole and missfiring.Worth a look. Remove the top plastic engine cover and remove the coil on number 1 and have a look down the hole. Water contamination should be obvious.

That engine does not suffer with oil contamination so you can rule that out completely.

Get a cylinder leak check done.

Thanks Oliver

Do you mean remove the spark plug? If not what is the coil?

Lastly if there is water contamination what would I see?

 

[JC180]

P0171 is the P code you should be looking at, fault will be with an intake or exhaust leak, Airflow sensor, fuel pressure, faulty injector or lambda sensor. Take the car to someone who has the ability to read and interpret the fault codes and do the neccessary test work afterwards.

Thanks but the indie have been a little cluless/unwilling to help even though they have the diagnostic equipment. They seemed happy enough to take my credit card though when they cried out in unison that is was the MAS!

All they are telling me now is that they will knock out the lamp one last time but it will come back on.

 

[JC180]

That engine does not suffer with oil contamination so you can rule that out completely.

But isn't the 271 engine the one that suffers with this? i.e. the Kompressor engines?

 

[BlackC55]

The 271 engine in your car suffers with poor valve seating causing the engine control unit to pick it up bringing the light on.

The fault code you have points directly towards this.

The remedy is either to re-seat the valves or a new cylinder head (complete). To date I have done both with sucess.

 

[BlackC55]

But isn't the 271 engine the one that suffers with this? i.e. the Kompressor engines?

NO. That is the 111 engine. Very different.

 

[JC180]

The 271 engine in your car suffers with poor valve seating causing the engine control unit to pick it up bringing the light on.

The fault code you have points directly towards this.

The remedy is either to re-seat the valves or a new cylinder head (complete). To date I have done both with sucess.

Eeek complete cylinder head...

How easy (cheap) is it to reseat the valves?

 

[BlackC55]

Thanks Oliver

Do you mean remove the spark plug? If not what is the coil?

Lastly if there is water contamination what would I see?

The coil is the device that fits onto the spark plug.

If there has been water in there it shows a white residue.

 

[BlackC55]

Eeek complete cylinder head...

How easy (cheap) is it to reseat the valves?

BTW I am telling you worst case senario.

R&R cylinder head 9+hrs

R& re-seat valves 2ish hrs

Of course this may not be the problem. Take it somewhere where they no what they are doing. I am only giving you suggestions.


(I have yet to fit an air mass sensor to a 271 engine since they have been in production)

 

[JC180]

Thanks Ollie

I am going back to the indie tomorrow and will politely request they check this out for me.

Intersting you have never fitted a MAS to a 271 engine, they were telling me they have done loads. For the record I wish you lived closer as I would trust them as far as I could throw them! You ever heard of a faulty MAS? They were telling me one failed within 3 weeks and needed relpacing. I reckon this story was to cover their backs if my light came back on as they never did replace mine

 

[BlackC55]

Air mass replacement is MEGA common but not on the 271 engine.

 

[tech123]

check the partial load vent hose. they tend to split and draw in air. you need to remove the airbox and control unit assembly to check it.

 

[JC180]

check the partial load vent hose. they tend to split and draw in air. you need to remove the airbox and control unit assembly to check it.

Thanks tech

Another thing to highlight for them to check. Thanks for your input.

 

[BlackC55]

That partial vent hose normally brings on running faults such as hunting but you have no symtoms

 

[JC180]

Ok all grateful thanks for all your kind input.

WAS meant to take it in to the indie yesterday but they were too busy. I am going away for the weekend and wanted it sorted prior.

SO I took it in to Mercedes Whitefield this morning and straight away they said I had a split Kompressor hose. They said they had one in stock and it would be 2hrs labour. In the end it was 2.5hrs (they only charged me for 2) and the part was just a fiver. They gave me an overall 10% discount and was left with a bill for £236. Stuart Hall the service manager was really helpful and overall a great experience from a dealer.

Money wasted at an indie, 0 Good dealer service 1

Here's to hoping they keep it up.

Oh one further thing 2hrs to replace a Kompressor hose?? It is underneath the airbox but would they need to remove the MAS and ECU to get at it (1" rubber hose)? Ollie you'll know for sure. Is it reasonable. I suppose it stays at 0 - 0 until I have this confirmed