MAKE STICKY: Rough idle when stopped in gear. Check this first
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Joined: May 2025
Posts: 24
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CLK320 & C240
MAKE STICKY: Rough idle when stopped in gear. Check this first
I've read so many threads online regarding a problem where the car intermittently idles rough when stopped and in gear. You throw it into neutral and it stops. Most of the fixes suggest it's likely one or both motor mounts. I'd done a deep dive online reading every post I could find regarding the same issue with my low mileage '02 C240. I ordered some replacement motor mounts, and a special offset 16mm wrench, and was planning on doing the work next weekend.
Then I saw this video yesterday after narrowing my search terms. Turns out it's actually related to a petrified air cleaner box / engine cover / MAF seal
that no longer seals properly. I went to the car immed. and took the engine cover off and adjusted the way it sits on the MAF and BANG!, no more vibration when stopped and in gear.
I'm really curious how many $Millions of $ have been spent over the years tracing this problem. Every shop must know about the issue. The reason it doesn't fit properly on my car is because the main cover actually bumps into the oil filler cap and with the petrified seal there's no wiggle room. BTW on my C240 you can't fit your hands in behind the MAF area unless you are 95 lbs.
FFWD to about 2:10 in the video
.
Then I saw this video yesterday after narrowing my search terms. Turns out it's actually related to a petrified air cleaner box / engine cover / MAF seal
that no longer seals properly. I went to the car immed. and took the engine cover off and adjusted the way it sits on the MAF and BANG!, no more vibration when stopped and in gear.
I'm really curious how many $Millions of $ have been spent over the years tracing this problem. Every shop must know about the issue. The reason it doesn't fit properly on my car is because the main cover actually bumps into the oil filler cap and with the petrified seal there's no wiggle room. BTW on my C240 you can't fit your hands in behind the MAF area unless you are 95 lbs.
FFWD to about 2:10 in the video
.
Last edited by swwalker; Jul 12, 2025 at 07:51 PM.
Joined: Nov 2016
Posts: 7,847
Likes: 3,495
From: Maryland
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
I've read so many threads online regarding a problem where the car intermittently idles rough when stopped and in gear. You throw it into neutral and it stops. Most of the fixes suggest it's likely one or both motor mounts. I'd done a deep dive online reading every post I could find regarding the same issue with my low mileage '02 C240. I ordered some replacement motor mounts, and a special offset 16mm wrench, and was planning on doing the work next weekend.
Then I saw this video yesterday after narrowing my search terms. Turns out it's actually related to a petrified air cleaner box / engine cover / MAF seal
that no longer seals properly. I went to the car immed. and took the engine cover off and adjusted the way it sits on the MAF and BANG!, no more vibration when stopped and in gear.
I'm really curious how many $Millions of $ have been spent over the years tracing this problem. Every shop must know about the issue. The reason it doesn't fit properly on my car is because the main cover actually bumps into the oil filler cap and with the petrified seal there's no wiggle room. BTW on my C240 you can't fit your hands in behind the MAF area unless you are 95 lbs.
FFWD to about 2:10 in the video
.
https://www.youtube.com/watch?v=DjCwfJFUz0A&t=289s
Then I saw this video yesterday after narrowing my search terms. Turns out it's actually related to a petrified air cleaner box / engine cover / MAF seal
that no longer seals properly. I went to the car immed. and took the engine cover off and adjusted the way it sits on the MAF and BANG!, no more vibration when stopped and in gear.
I'm really curious how many $Millions of $ have been spent over the years tracing this problem. Every shop must know about the issue. The reason it doesn't fit properly on my car is because the main cover actually bumps into the oil filler cap and with the petrified seal there's no wiggle room. BTW on my C240 you can't fit your hands in behind the MAF area unless you are 95 lbs.
FFWD to about 2:10 in the video
.
https://www.youtube.com/watch?v=DjCwfJFUz0A&t=289s
