01 200 Komp, possible O2 sensor problem? - Monsieur Kev
I have a 2001 CLK 200 Komp with 69,000 miles so far, that I bought secondhand two years ago. Within a couple of weeks after buying it the engine warning light came on although the car seemed to drive OK. O2 sensor was diagnosed by MB garage, but the car had only had a new one fitted six months previously so another one was installed under warranty.

18 months later after only having covered 8,000 miles since the new sensor I went to start the car the other day. It started and ran fine for about 5 seconds but then the engine seemed to jump/surge and ran on three cylinders, so I switched it off. I started the car again and it ran OK but the yellow engine warning light on the bottom right of the instrument cluster has stayed on.

Anyone an idea what this may be and would it be OK to drive the car 25 miles to my nearest MB garage?


Moved over to Tech and year/engine details edited in,

Edited by Pugugly on 31/10/2008 at 20:52

01 200 Komp, possible O2 sensor problem? - Screwloose

There are 3,000 possible reasons why that light is on; it should be OK to drive - although it may be in limp mode if the fault is serious.

Most oxygen sensors that are replaced have nothing wrong with them. There are a plethora of codes that have "oxygen sensor" mentioned in their definition - but usually it's just reporting, correctly, that there's a mixture fault of some type.

Changing the healthy sensor and not addressing the underlying fault, just means an eventual repeat of the same code.
01 200 Komp, possible O2 sensor problem? - Monsieur Kev
Thanks very much
01 200 Komp, possible O2 sensor problem? - topbloke
its just guessing, the only real thing that you can do is have the codes read, you say that it seem to run on three cylinders then the light came on its possible that it would have a missfire code, if so it should say which cyl, get the codes read then repost the findings back here
01 200 Komp, possible O2 sensor problem? - Monsieur Kev
I finally got the car into the Mercedes dealer in Boulogne today, Tuesday 25th November. The car was serviced there back in May and has only covered 1,500 miles since then. I asked them at the time to check the spark plugs, because I did not know whether they had ever been changed. I was told they were OK.

The car has driven well since the original hiccup but of course the warning light was still on.

Today the car clocked up 80,000 miles as I drove to Boulogne. The car was given a diagnostic check and the mechanic brought out the spark plugs. Shot to pieces! The mechanic said they were the original set.

I had a moan about the fact I had asked them to check the "bougies", so they discounted the bill.

Anyway new set fitted, E157.00 put on my credit card, and it is driving lovely again. Just the MOT to pass on Friday.

Edited by Monsieur Kev on 25/11/2008 at 21:06

01 200 Komp, possible O2 sensor problem? - Screwloose

Thanks for the update; so the plugs were worn out and the oxygen sensor was - correctly - reporting an excess of oxygen caused by the misfire.

They shot the messenger - again.
01 200 Komp, possible O2 sensor problem? - Monsieur Kev
Yes Screwloose, you were spot on. Many thanks.

The underlying fault was the plugs, but the car had two new O2 sensors fitted by a Merc dealership in Wiltshire: one by the owner before me with a bill totalling £383.00, £190.00 of which was labour. Another O2 sensor (so they said) was fitted by the same garage under warranty when the light came on again within 6 months, by which time I owned the car.

The French mechanic showed me the plugs and they were black and knackered. How often should these 'long life' plugs be changed. With my car they seem to have been left in too long.

Driving it today although it seemed OK before and after the misfire incident, the new plugs have made quite an improvement, plus the fuel consumption according to the computer is averaging 2 to 3 mpg better.

While you are here Screwloose, is there anything else I should check for or change on this car? It has had new front discs,pads and ball joints. Rest of it appears really good for 70,000 miles.

Edited by Monsieur Kev on 27/11/2008 at 00:25

01 200 Komp, possible O2 sensor problem? - Screwloose

For a W208 200K; the plugs should be changed at any major service if they've done between 18-27,000mls [30-45,000Kms] - or 4 years max.

As you've found; old plugs cost fuel and long change intervals don't save anything.

If it's had dealer servicing from new, then they should be on top of anything that needs changing. [In theory...]

01 200 Komp, possible O2 sensor problem? - Monsieur Kev
One last thing Screwloose, these platinum tipped (or iridium?) plugs are costly, what are the best spark plugs?

As you said, it is better to change them more often, so are 'long life' plugs necessary?

And yes it has always had MB service history. In fact it has had more services than strictly necessary, so I am disappointed that the car virtually broke down because MB service procedures on both sides of the Channel, appear to be lacking.

Edited by Monsieur Kev on 27/11/2008 at 09:31

01 200 Komp, possible O2 sensor problem? - Screwloose

My listing [for the 111.956 engine] is Bosch F7KTCR; a change at 20,000mls isn't excessive for those.
01 200 Komp, possible O2 sensor problem? - Monsieur Kev
I am not sure whether there has been a debate about spark plugs for the 200 and 230 Kompressor engine before, but you are right again Screwloose that the Bosch Bosch F7KTCR copper plugs are the one for my engine.

What on earth did I have before which were in use for the last seven and a half years and knocked up 80,000 miles from new? Were the original plugs platinum? And I wonder what has been fitted now?

If only I had known this before as I have been charged around 100 Euros for four plugs. Would they be MB ones?

It will take me a while to get to 20,000 miles, so will ask the question later about how to fit plugs on my engine. Looks a bit daunting.
01 200 Komp, possible O2 sensor problem? - Screwloose

Did the originals really go that far? Only very special plugs have that sort of lifespan - especially on a supercharged engine?

It's because spark plugs have become a bit of a mission that they get ignored. In the old days, they were a nice profit-earner and would be changed as soon as justifiable.

At 25 euro each; I'd hope they were MB-boxed ones....

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