Hi all,

We're new to the SLK and have been reading the forum to get some usefull tips!

Now, we have our first significant problem and wondered if any of you guys can help...

When the car is up to temperature and you slow to a stop (at a stop signal for example) the engine will often judder and stall. (If you slip it into neutral the lack of resistance allows it to pick up again before it stalls)

Recently, we had the car serviced and the garage noticed the problem following the service. They said that they then cleaned out the throttle housing as this is often the cause of the problem but that has had no effect.

We have been told to run the car and see if the problem goes away (fantastic advice!!) but obviously I am not convinced this will work.

Has anyone got any idea where we should start with trying to trace this problem before the garage start replacing expensive parts...?!

Thanks in advance, Si and Kate

 

Gooday.

What vehicle model and year do you own??

Maybe CPS, dirty MAF, K40 relay pcd dry joint....

Bazzle

 

Hi Bazzle,

We have a '99 230K, standard as far as we can tell except for an after-market exhaust.

Thanks for the tips so far, I will start looking for translations of the terms you've used!!

I have read alot about this K40 relay being a source of problems. Are these the sort of symptoms that you expect with a faliure of this component?

Cheers, Si

 

I vote for fuel contaminants, a dirty air and or fuel filter, or a dirty MAF (going bad?). Has someone pulled the on board computer codes? How many miles are on this vehicle? Spark plugs need service? Regular things that can happen to any vehicle.

 

I advise that you get the codes (if any) read since this will narrow the possible causes.
In addition some history regarding when problem started. Was it present BEFORE the car was serviced, or only AFTERWARDS?
If afterwards understanding exactly what they did will help. MB dealer or regular fix it garage?

Cleaned the throttle body....unusual action to take! Did they mean the MAF Mass AirFlow sensor. .

Mileage?
When was the non OE exhaust fitted and are the cats still in place? This could cause the problem but if the car has run OK since fitment it can be eliminated.

Is the Check Engine Light CEL on? (Check it works when you turn the ignition on before starting the car.)

At the moment could be any number of things but on the most common problem list are:

K40 (MB coding number) Small relatively inexpensive relay in black box at back of engine compartment. Controls fuel supply. Known to have intermittent operation due to poor manufacture. However symptoms don't quite fit. Usually associated with no start.

MAF. Out of tolerance (approx 200 USD occurs at about 70k miles) but this would set a code and or turn the CEL on.

Plugs, when were these changed and are they OE?

..........

What are the cold and warm out of gear idle speeds? Auto or Manual? Should be something like 1000 / 700 without looking them up.

If its got a non OE exhaust I wonder if any body has tampered with the amount of supercharger boost? Again, when did the problem start.

First step whilst you arrange for the codes to be read is to use up the existing fuel and refuel..... JUST IN CASE it is contaminated fuel.

You will see that we are all saying the same thing. Common problem but many potential causes.

Stuart

 

Thanks for this Stuart

OK to try and answer some of your q's...

Bearing in mind we have only driven 300 miles or so in the car, we think the problem was created after the last service by our local regular garage (So far these guys have serviced our previous Audis/Mercs without any problems)

Looking through the paperwork with the car, there is a receipt for 'MA000 094 09 48 AIRMASS' for £246 ($400??) and an hour's labour at MB from this time last year.

I have no record of how long the exhaust has been on the car, but the cats are there as I have just put it through the annual emmisions test.

Plugs were changed last week during the service. The garage usually uses Bosch or similar, I'll look into it.

The car is an auto. When it's cold it idles at around 900rpm and when warm, nearer 600-700.

One question, are there any tell-tales that someone has tinkered with the supercharger?


Like you say, next steps - flush the fuel and book into have the codes read.

It sounds like it needs to go see an expert!!

I certainly see what you are saying... Arrrggh!

 

Hi Si,
See you live in Ashby. I'm at Stafford. Send me a PM and I'll provide address.
Will read codes for you (free) if you would like. Only a few minutes job and it may provide the clue you are looking for. If not MB will charge £25 ish.
You didn't state whether CEL was on. I assume not.
I'm suspicious since MAF was changed only last year. If done by MB it will have been OE so guess that this isn't the problem £240 sounds about the MB price for the job. I wonder if they were trying to resolve the cut out problem.
Suggest you get the K40 and fit it yourself. Low cost.
Any chance of getting some past history from the previous owner.
Stuart

 

Read
https://mercedesforum.com/m_60731/mp..._/tm.htm#62068
Another two satisfied "customers".
Stuart

 

Thanks for all this good advice!!

I spoke to the MB parts department on the phone yesterday to try and order the K40 relay.

However the guy on the other end of the line wasn't aware of a K40 relay for an SLK.

Sorry to sound like a complete doughnut but does anyone know the MB part number for this relay so that I can help the old boy out and hopefully get hold of the holy grail itself?!

Cheers, Si

 

Hi,
Sorry i don't have the part number. try asking the guy for a fuel pump relay and see if you get more luck.
Ready and waiting to read your codes.
Stuart