Lambda Problem SLK230

[shineydave]

Hi all, first time post so be gentle with me.
an accountant friend of mine has a 2003 SLK230. over the last 8 or 10 months she's had 3 Lambdas fitted and has just rung me to say it needs a fourth. now i'm no MB expert but i think i'm smart enough to deduce that her mechanic has been tackling the symptom and not the root cause as i think she would be highly unlucky to have four Lambdas fail without there being some other problem causing the failure.

so i have a couple of questions before i have a look at it, hopefully you guys will have some experience that you will be kind enough to share with me.

1. i've done a search through the forums and can't find anything specific to the SLK230 but have noticed mention that many MB cars have 2 Lambdas, one before and one after the cat, is this the same on the SLK as i'm wondering if her mechanic has been changing the wrong one.

2. has anyone else any experience of so many failures. my experience tells me that other than old age a Lambda can fail because of a rich mixture or contamination, any thoughts?

thanks for listening

 

[television]

http://www.detali.ru/cat/oem_mb2.as...GM=716.667&CT=F&cat=69J&SID=49&SGR=210&SGN=02

they are all listed and where they are.

What was wrong with the car

 

[Uncle Benz]

Seems to me like you could be right about fixing the symptom...

How long before the engine warning light comes on again after replacement??

Hopefully a long shot, but there is a known problem with oil getting into the ECU from wiring to camshaft adjuster solenoid. This often brings up a fault code relating to lambda sensor, but it is caused by the oil getting into that part of the ecu circuitry that deals with lambda control.

Other possibilities are failed cat, overfuelling, plenty of others too...

 

[television]

Seems to me like you could be right about fixing the symptom...

How long before the engine warning light comes on again after replacement??

Hopefully a long shot, but there is a known problem with oil getting into the ECU from wiring to camshaft adjuster solenoid. This often brings up a fault code relating to lambda sensor, but it is caused by the oil getting into that part of the ecu circuitry that deals with lambda control.

Other possibilities are failed cat, overfuelling, plenty of others too...

I think that your long shot is very good

 

[shineydave]

it seems that the only reason she's changing the Lambda is because her mechanic is telling her it's faulty after scanning the car, she says she doesn't feel any difference in the way it drives nor does it illuminate the CEL.

i'll have a look at the ECU wiring for oil contamination, if it's oiled up is it just a matter of cleaning or will the ECU be toast?. any easy ways to spot a blocked cat on these cars?. it seems that it drives perfectly other than her mechanics insistance that the Lambda has failed.

another interesting point since it doesn't light up the CEL. i notice from the drawings (thanks for the link Television) the rear Lambda is listed as "diagnostic". my assumption is this sensor is used to confirm the efficiency of the cat rather than provide info for the ECU to alter fuelling. if this is the case then would a failure of this Lambda throw a CEL. i'm begining to suspect her mechanic has seen the DTC for it and got his wires crossed as to which sensor to change.

thanks for the responses gents

 

[Uncle Benz]

I think you need to take this car to another mechanic. The second sensor is to confirm correct catalyst operation, but will throw a cel if faulty, or if cat not functioning as per spec.

To check for oil contamination, the quickest way is to take off the front cover on the end of the cam box area, pull off the electical plug and look for oil. It is no guarantee that oil has made it as far as the ecu, but will give a clue. If this is the fault, a live data check will probably show no activity from one of the lambda sensors.

In my experience, a faulty MAS can throw up a fault code relating to lambda sensor adaptation, since a faulty MAS can affect the amount of fuel metered, and hence the mixture the lambda is measuring.

Back to my first comment - a decent indy who knows what he is doing, and has the experience to interpret what the scan tool is telling him will be able to sort this for you. I feel it is becoming less and less likely that the lambda sensors are faulty at all.

 

[television]

I think you need to take this car to another mechanic. The second sensor is to confirm correct catalyst operation, but will throw a cel if faulty, or if cat not functioning as per spec.

To check for oil contamination, the quickest way is to take off the front cover on the end of the cam box area, pull off the electical plug and look for oil. It is no guarantee that oil has made it as far as the ecu, but will give a clue. If this is the fault, a live data check will probably show no activity from one of the lambda sensors.

In my experience, a faulty MAS can throw up a fault code relating to lambda sensor adaptation, since a faulty MAS can affect the amount of fuel metered, and hence the mixture the lambda is measuring.

Back to my first comment - a decent indy who knows what he is doing, and has the experience to interpret what the scan tool is telling him will be able to sort this for you. I feel it is becoming less and less likely that the lambda sensors are faulty at all.

Thank you for the above post

 

[shineydave]

Thanks for the replies.

I'm going to have a look at it this week myself, i've quite a bit of experience with fuel injection and control systems so hopefully i'll be able to get to the bottom of it. i actually suspected the MAS as i've had a similar problem previously on my Audi S4 where Vag-Com indicated a Lambda out of tolerance fault where in fact it was the mass airflow sensor that had failed. the mass airflow meter rarely shows a fault so unless you could look at the readings and realise they were out of tolerance you'd automatically go to the Lambda and swap out the symptym rather than search deeper to find the root cause.

i'm still at a loss to understand why there's no CEL lit or why the car drives perfectly. previous issues with Lambdas and mass airflow sensors have generally manifested themselves with driveabillity issues. i'm begining to suspect he's just trying it on with her.

assuming the MAS is faulty, on the S4 for example, i can unplug it and i can hear the engine note change as the ECU reverts to the limp home map, would it be fair to say that if the MAS is faulty and i unplug it i wouldn't hear a change as the ECU would already be running in limp mode?

 

[television]

O2 sensors can and do turn the engine lamp on where as MAF sensors hardly ever do, yes you can unplug the MAF and see if there is any difference in the running

 

[Glenn Smith]

i'm still at a loss to understand why there's no CEL lit or why the car drives perfectly. previous issues with Lambdas and mass airflow sensors have generally manifested themselves with driveabillity issues. i'm begining to suspect he's just trying it on with her.

assuming the MAS is faulty, on the S4 for example, i can unplug it and i can hear the engine note change as the ECU reverts to the limp home map, would it be fair to say that if the MAS is faulty and i unplug it i wouldn't hear a change as the ECU would already be running in limp mode?

Sounds like theres a con going on, has she mentioned to the garage that the vehicle has already had 3 lambdas fitted, may be the fault is not being erased, check for cracks in exhaust manifold as these can cause problems with cats and lambdas. the only way to check the MAS is to drive at various engine speeds whilst comparing specification, with our VW engines (diesels) the only fault you got was lack of power, often partially corrected by disconnecting, substitution being the only real way of proving as it is difficult to drive and check theoretical with actual figures, mas readings can also be affected by air leaks and EGR problems.
One posssible reason for the fault, assuming emmissions and performance are ok, could be a loose wiring or corroded terminal causing intermittant failure and recording a fault, depending on how advanced the diagnostis are that is being used, they can tell how many times a fault occurred and excactly what condition the engine was in at the time of the last event eg eng temp, load, rpm etc.

 

[Shala]

I've had the MAF changed in november last year & while my car can go over 60mph & 3k revs now its still running uneconomical. The guy at the MOT had to rev the engine alot to pass the MOT. I noticed myself that the cars drinking alot of petrol as I'm a granny driver now (since I crashed my FTO on the motorway)

I had an auto-electrician look at it & he first said its the CAT. then he looker further into it and said its the LAMBDA sensor. He had a smartbox he used and this is what it came up with.
----------------------------------
Total codes: 001
CODE001:
P0130 G3/4 (02-CAT front right)
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I've spent alot of money trying to sort this car out. 1st the MAF then this. Can anyone confirm if its really the LAMBDA sensor I need to replaced.

 

[Shala]

any help?

any help please????

Shala