Help! Rough Idle on start up
Thread Starter
MBWorld Fanatic!
Joined: Jun 2011
Posts: 3,318
Likes: 171
From: Silicon Valley, CA
C63 AMG, P30
Help! Rough Idle on start up
Hi all,
This has happened a couple of times now. I go start the car, and the car just idles a bit rough. Nothing too extreme, but enough for the girlfriend to ask "what's going on?"
No codes, no CEL, nothing. Car drives and pulls well all the time and starts up well 98% of the time!
Any ideas on what to look for?
Thank you!
This has happened a couple of times now. I go start the car, and the car just idles a bit rough. Nothing too extreme, but enough for the girlfriend to ask "what's going on?"
No codes, no CEL, nothing. Car drives and pulls well all the time and starts up well 98% of the time!
Any ideas on what to look for?
Thank you!
Super Member
Joined: Dec 2012
Posts: 600
Likes: 6
From: Bay Area
2010 C63 P31 AMG
Hi all,
This has happened a couple of times now. I go start the car, and the car just idles a bit rough. Nothing too extreme, but enough for the girlfriend to ask "what's going on?"
No codes, no CEL, nothing. Car drives and pulls well all the time and starts up well 98% of the time!
Any ideas on what to look for?
Thank you!
This has happened a couple of times now. I go start the car, and the car just idles a bit rough. Nothing too extreme, but enough for the girlfriend to ask "what's going on?"
No codes, no CEL, nothing. Car drives and pulls well all the time and starts up well 98% of the time!
Any ideas on what to look for?
Thank you!
MBWorld Fanatic!
Joined: Sep 2005
Posts: 3,165
Likes: 59
C63 AMG P30 *EuroCharged*| Porsche Cayenne | Buell XB9SX
Just a question, what's the deal with winter blend and summer blend? Why don't we just have "gas"? Seems like the blends are the cause of issues with our cars.
Super Member
Joined: Dec 2012
Posts: 600
Likes: 6
From: Bay Area
2010 C63 P31 AMG
I believe it's mostly for enviornmental emissions issues that states switch between blends. exhaust gases from vehicle react differently in warm and cold climates...additives are added in winter blend that allow for a higher cleaner burn rate than summer blend. Plus I think this m156 or any Benz 8 cylinder has been sensitive to it for some reason. Benz has no fixes or are only temporary. I just changed gas and so far, no issues this winter. Chevron has least amount of ethanol in their blend so something to do with that I think.
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Past: 300zx TT 500hp Current: '12 C63
Sorry for bringing up an old thread, but for archival sake, Shell gas seemed to cause issues for me also. I was using Shell 91 (the highest they had near me at the time), and occasionally I would get a "running lean" CEL code. Not too long after that my fuel pump failed, apparently due to clogging.
Later, they introduced Shell 93 near me, and that seems to be better, but I would still get occasional rough idles briefly on start, but would otherwise drive great. Then I switched to Chevron 94, and it seems to run nicer, and also get slightly better fuel mileage. For the record I'm in Vancouver, BC
Later, they introduced Shell 93 near me, and that seems to be better, but I would still get occasional rough idles briefly on start, but would otherwise drive great. Then I switched to Chevron 94, and it seems to run nicer, and also get slightly better fuel mileage. For the record I'm in Vancouver, BC
Super Member
Joined: Dec 2012
Posts: 600
Likes: 6
From: Bay Area
2010 C63 P31 AMG
Sorry for bringing up an old thread, but for archival sake, Shell gas seemed to cause issues for me also. I was using Shell 91 (the highest they had near me at the time), and occasionally I would get a "running lean" CEL code. Not too long after that my fuel pump failed, apparently due to clogging.
Later, they introduced Shell 93 near me, and that seems to be better, but I would still get occasional rough idles briefly on start, but would otherwise drive great. Then I switched to Chevron 94, and it seems to run nicer, and also get slightly better fuel mileage. For the record I'm in Vancouver, BC
Later, they introduced Shell 93 near me, and that seems to be better, but I would still get occasional rough idles briefly on start, but would otherwise drive great. Then I switched to Chevron 94, and it seems to run nicer, and also get slightly better fuel mileage. For the record I'm in Vancouver, BC
After some time messing with the gas to resolve idle and code issue, there may a few things to consider other than gas. My issues were resolved when I replaced my PCV which tends to go out or start to around 40-50k miles from what I’ve gathered. Some resolved their issues by either reseating their intake box, checking if any air leaks before MAF, cleaning their MAFs, replacing intake manifold gasket due to leaks, replacing PCV (main one for me) and some other one off fixes.
Helped too to do a BG44 cleaner for the fuel system. All depends on how many miles and how you drive but it’s a great cleaner.
thanks for input and great on the Chev 94….it’s what dreams are made off here in CA
