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Discussion Starter #1
SLK 230 has a lack of power from the supercharger. Drives fine but when pedal depressed at speed can over-rev, lack of acceleration, sometimes lurches up into gear. Car has lost speed.


Pressure test (supercharger) shows it is only half the pressure level it should be. No obvious problems, hoses etc... all fine. Valve (within hose block) is also working and engaging correctly. Unsure as to why pressure is down so much.


Possibly slipping belt? Seems unlikely, but possible at over 100K miles. Front of supercharger is loose which is (apparently) strange but all is engaging and running correctly while car stands still and is manually revved.


Car has been into the garage today but they could not find the fault either. Guy worked at Merc for years and didn't charge me but he was a bit perplexed. May have to take to specialist with STAR kit - anyone know of one in Surrey (UK) who doesn't charge an arm and a leg?


Any thoughts on this problem would be great.
 

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Premium Member 2002 SLK230K
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If your lacking boost then there is a disconnected/cracked hose, dirty MAF or a disconnected hose from the oil separator to the air intake manifold.
 

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Discussion Starter #3
Thanks, will clean the MAF for now and replace at next service. Having now read other people's problems/symptoms, the MAF seems to be the cause - I know hoses are fine.


Will I need the error codes erased from the computer or is that a myth? I can just disconnect the battery for 20 minutes to do that tbh but I am not convinced - can you advise? Thanks.
 

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Thanks, will clean the MAF for now and replace at next service. Having now read other people's problems/symptoms, the MAF seems to be the cause - I know hoses are fine.


Will I need thze error codes erased from the computer or is that a myth? I can just disconnect the battery for 20 minutes to do that tbh but I am not convinced - can you advise? Thanks.
I think these cars are drive by wire and can sometimes need to be reset or replaced. To reset you can remove the negative battery terminal for 30 seconds. It can also be tested by some OBD scanners that show throttle position percent.

As far as erasing codes, I don't know. I think every car owner should have an OBD scanner.
 

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Discussion Starter #5
Thanks, I spoke to Merc Medic, parameters will need resetting to the new unit for the internal CPU so I just buy the MAF off ebay, take it along and they charge 30 minutes labour to fit it (and a new air filter) and reset the parameters using the diagnostic kit. Seems reasonable. Car is running perfectly now though so maybe the pressure test the guy did has cleared some kind of obstruction? No idea anymore. Intermittently the key fob still stops working and I have to manually unlock the car and turn off the alarm via the ignition. Doubt I will ever get to the bottom of that issue either.
 

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Discussion Starter #6
I have worked out what was wrong with my car. I tested the theory three times and each time it caused the problem.


Shell fuel. Higher octane or normal unleaded, my car hates the Shell fuel and I get all the above issues. Supermarket fuel (95 unleaded)however, it runs great. I guess it cannot cope with the change in octane levels or that cleaner stuff they put in the shell fuel or something after so long, anyway it completely buggers the car up - so its cheap fuel only and definitely NOT from Shell from now on.
 

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Premium Member 2002 SLK230K
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Be careful with the MAF from ebay, there have been lots of complaints that they don't work properly. Best bet if you can is get one from your dealer.
 

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Discussion Starter #8
A Bosch MAF is a Bosch MAF. Anyway, it seemed to be a fuel issue as I explained.
 
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