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Discussion Starter #1
Hi all,

I've got a 230k 2002, runs like a dream and I use it daily in all weather!

Recently it came up with the engine management light which turned out to be a MAF fault. That was replaced and all was well except...

On cold start, it would start and run fine but if I drove it from cold, it had a hell of a hesitation. Pushing the pedal down further pushed it passed it and when it got warm, the problem was less noticeable to the point it disappeared.

Now today, the engine management light is back on.. fault code is P201D-004:

Self adaption of mixture formulation, Mixture is too rich at idle speed P0172

Did a search on the problem but coming up with various possibilities.. anyone else had this issue or know what it could be?

Cheers
 

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Premium Member 2005 SLK55 AMG; 2005 SLK350
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Do all of your injectors sound relatively the same if you listen with an automotive stethescope? Was it an OEM MAF you installed, or a knock-off? And do you have a way to test the fuel pressure at the rail?
 

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Discussion Starter #3
Thanks for the reply. The MAF was bought from a reputable part chain here, not Mercedes. The CEL for the MAF and any codes have gone since it's replacement.

All injectors sound the same, the car runs perfectly, it's just the stutter at low revs and start off speed. Haven't tested fuel pressure, not sure that would be a problem as it's running rich and drives well throughout the rev range (with exception to this issue).

It honestly feels like an accelerator pedal issue, like the potentiometer in the pedal has failed but I'm guessing that would give a different code, not the one I have got. I have tried the pedal reset procedure but that didn't seem to make the issue go away.
 

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Premium Member 2005 SLK55 AMG; 2005 SLK350
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Well I'm totally guessing. It's possible you have a pedal issue but I don't see why it would be related to engine temp. And I definitely don't see how the pedal could cause running too rich.
 
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