Posting on behalf of a mate.

 

He got a cheap supercharged SLK from a bloke at work and it needed an MOT recently and has failed massively on emissions.  I've driven it and it seems underpowered, not like any supercharged car I hgave driven before.  Also fuel economy is bad.

 

Anyone had one before?  Similar issues?  Any suggestions?

 

Any help greatly appreciated

Tbh they don't feel particularly great even when running perfectly. Emissions could could a simple sensor through to many other faults. Has he tried putting some reddex through? Back road blast to clear any rubbish in the exhaust?

Both Lamda sensors have been changed and it had the "italian tune up" (a good thrashing).

 

Next up is a couple of shots of carb cleaner through the intake and a new air filter.

Seeing an 'Independent Mercedes Specialist' would be a good move. Possibly Money well spent.

 

These cars and even newer ones are dirt cheap not only because of Fuel Consumption,

 but because a cheap fix does not always get them through a MOT.

 

If Italian Tune ups & some Wynns products and the likes were all that was needed to keep them on the road 

would more of us not be driving these cars that can be bought for 'Much Cheapness'.

All that says Supercharged (Kompressor) is not Gold.

 

george

What are the emissions results?

The numbers are:
CO 8.79% (fail)
CO2 3.4%
O2 2.73%
HC 302ppm (fail)
Lambda 0.764 (fail)
 

Lambda sensor issues (compare individual probe voltages agaisnt spec and each other: If pre and post cat are the same suspect a cat failure) may well cause the CO and HC readings out of spec, and high fuel consumption.

 

Also check engine temperature readings at EMS (I presume Merc diagnostics can do this?) in case it's running permanently in cold enrichment.

Other outside possibility - Is it using lots of oil?

Is that on idle or fast idle? Have you got both sets of results?

 

If the lambda sensor(s) are good, those readings indicate a lot of overfuelling.

 

I know nothing about SLK Kompressors but would point you in the direction of the aforementioned "indie specialists". You need to know if the engine is getting up to temperature, that the car knows that, that the MAF, if any, is working properly. Would also suggest checking/changing the plugs.

I did a google 

 

slk world mot fail emissions

 

people in threads that come up there seem to know the subject

Thanks, it's probably his thread you found!!