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Discussion Starter #1 (Edited)
Hi all,

Your help is desperately needed!

Vehicle details:
Mercedes SLK 200 (Manual transmission)
2001 (R170 Engine)
2000cc, Supercharged

-Car has reduced power (approximately 60% of normal power). It is possibly in limp mode, or is not supercharging (however you can still hear the supercharger clutch engaging when necessary revs are reached).

-It has no ‘consistent’ warning lights lit on the dash. Most of the time the engine warning light is lit, however it can run with reduced power with no warning lights lit. Generally after the code is cleared, it will run with reduced power for a few days before the engine light comes on again (can the car go into limp mode without any warning lights?).

-Garage said the code was a Mass Air Flow error and the MAF sensor needed replacing. Unfortunately I don't have the actual codes, but I can go back to the garage to get them if required.

-The first time the problem occurred, I removed and cleaned the MAF sensor and the car ran fine for about a month. The second time it happened, the garage installed a brand new MAF sensor and cleared the warning code. The same problem occurred within a few days.

-Sometimes it will start-up and drive fine with normal power. Most of the time it starts-up with reduced power. It never changes whilst the engine is running – it either starts up with full power or reduced power, and remains at that level until it is switched off.

-Returned it to the garage, who this time said that the “supercharger throttle plate” was dirty and sticking, and had therefore been cleaned. They also cleared the warning code again. A couple of days later the problem occurred again.

-It idles fine, with no shuddering regardless of power output.


The garage clearly don’t know what the issue is, however as I paid them to initially fix the car I need to return it to them to have it fixed under warranty rather than pay a different garage. I’ve trawled the internet and this forum, and while a lot of people seem to have problems with the MAF sensor, I can’t seem to find anyone with an identical problem. I am actually thinking the MAF sensor has not got anything to do with it. Any ideas would be appreciated.

Cheers.

Nick.
 

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Premium Member 2004 SLK200K
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10,761 Posts
The K40 relay gives a lot of running problems on the r170 due to corroded/bad solders , try a search ??
 

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Registered 2001 SLK200
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634 Posts
This engine is shared with the more common C and CLK classes. Try searching for this issue on the MB world forum.
 

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Premium Member 2005 SLK55 AMG; 2005 SLK350
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Go ahead and reflow the solder while you have it out... Even if it looks good. When you replaced the maf did you buy oem/bosch or another? And did you check the maf wiring visually?

Definitely sounds electrical....
 

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Discussion Starter #7
Update

Okay thanks for the replies, here is a quick update:

The two codes it is returning (as written by the garage) are:
-57 - Supercharger circulating flap emergency mode
-54 - Secondary air system air mass low

After a bit of googling, I have found that whenever Mercs throw up a code relating to the supercharger, they will automatically bypass the supercharger, which is presumably causing the reduced power.

The garage has said that they are unable to fix it as it requires reprogramming, and needs to be taken directly to a Mercedes garage?

Before I spend loads of money taking it to a Mercedes garage, has anyone got any idea what could be causing those fault codes?

Many thanks.
 

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Discussion Starter #8
Still ongoing ...

Well, I still have the problem of the reduced power.

I have just received the car back (last week) from an Independent Mercedes Specialist. I paid them to sort it out, as after diagnosing it with their STAR machine they seemed sure the lack of power was due to a carbon build-up in the inlet manifolds. They replaced the manifolds and gave the MAF sensor a clean out and stuff and then gave the car back. It ran fine for a day, and then I started it up the next morning and it was back to the reduced power again. Then a day or two later, the engine light came on again.

This time I borrowed a friends code reader and it was the same error :
P0410 - Secondary Air Injection System

I took at back to the Merc Specialist and he said he couldn't understand what the problem was, and this time all he has done is 'reset' everything and test-driven it 4 times. Irritatingly, it worked fine for the 4 occasions he drove it, but it is now back to the reduced power again.

I am completely at a loss now. Two separate garages have taken a look at it, one of which is a Merc Specialist, and clearly neither can diagnose it.

I can't believe I seem to have the only SLK in existence with this random problem?

Perhaps if anyone could answer this question it might help me:

-How would I know if the engine is in limp mode, or simply performing badly? (The reduced power can happen a few days before the engine light comes on).

Thanks all.
 

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poor acceration?

** edited to say that after reading your 'secondary air system' code i am sure i have the answer below:

Does your car bog down or misfire under acceration? Does it rev smoothly?

We had a problem where if we needed a quick kick down our car would pop and bang and give no power what so ever.

How i fixed this was to remove and replace the air oil separator and pipes attached to it. The pipes and separator were full of gunge.

We actually brought the parts from a local MB dealer and the prices were not bad at. It turned out to be an easy and cheap fix at just £66 when done by ourselves.

Have you tried this? It made a hell of a difference and our SLK runs sweet now so it might be worth a look as i am pretty sure it will sort your woes. :tu:
 
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