w221 Rough Idle
Thread Starter
Newbie
Joined: Mar 2024
Posts: 2
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S550
w221 Rough Idle
Recently I've been getting some REALLY rough idles from my s550. It's gotten to a point where the entire car feels like its rocking back and forth constantly at lights and only weakens but doesn't go away while driving. I've spoken to some people on the issue and they mention I might need to replace the EGR valve, PCV, or head gasket to fix the issue. So far I've only installed new spark plugs which didn't help. Has anyone had a similar issue or has any advice?
MBWorld Fanatic!
Joined: Aug 2014
Posts: 5,375
Likes: 1,693
S500
coil stick dead - infamous for failing - you don't need to do all 8 - some come from the die in 5 years parts bin, others are OK as they played mix and match for most markets. Using a mix of ones fitted to markets where they are still pretending to build a reputation and half from the reject pile of the parts supplier...
decent diagnostic kit will tell you EXACTLY which cyl is playing up - YOU MUST NOT DRIVE or ALLOW TO RUN LIKE THIS - IT WILL RUIN THE CATS AND NOT MANY MILES LATER TRASH THE ENGINE !!!
if you run android this will do it - https://play.google.com/store/apps/d...anmaster&hl=en you will ALSO need a competent OBD2 dongle - don't buy the cheapest on ebay - u will buy 5 or 6 before getting one that almost functions... ones worth owning are $40 to $70
vlinker have started making decent dongles that cope with much of the modern world - and ALWAYS load the latest firmware to the dongle - they discover every few months yet more tricks and cheats the manu build in to stop proper communication.... https://www.vgatemall.com/products-detail/i-52/ that one will do fords correctly but then not GM... they only just worked out the one you need to do Ford's correctly needs to fake 18V (FEPS) - either of these get you full BM capability (so you can code all the toys till it looks like a 3 year old played) but few will do GM Single wire CAN (that no one else bothered to use) - vlinker do a MC version to play on bikes correctly that also does GM https://www.vgatemall.com/products-detail/i-5/ )
One day when they work out how we'll be able to buy just one and it will do everything - but today there's isn't one out there - unless you go the $2000 route and even then its a lie....
the set up above (a decent app and a decent dongle) should be in the pocket of ANYONE ever starting ANY modern car or bike at ANY time.... they are that ALL that badly made - today its madness not to have it with you 24 7
.
decent diagnostic kit will tell you EXACTLY which cyl is playing up - YOU MUST NOT DRIVE or ALLOW TO RUN LIKE THIS - IT WILL RUIN THE CATS AND NOT MANY MILES LATER TRASH THE ENGINE !!!
if you run android this will do it - https://play.google.com/store/apps/d...anmaster&hl=en you will ALSO need a competent OBD2 dongle - don't buy the cheapest on ebay - u will buy 5 or 6 before getting one that almost functions... ones worth owning are $40 to $70
vlinker have started making decent dongles that cope with much of the modern world - and ALWAYS load the latest firmware to the dongle - they discover every few months yet more tricks and cheats the manu build in to stop proper communication.... https://www.vgatemall.com/products-detail/i-52/ that one will do fords correctly but then not GM... they only just worked out the one you need to do Ford's correctly needs to fake 18V (FEPS) - either of these get you full BM capability (so you can code all the toys till it looks like a 3 year old played) but few will do GM Single wire CAN (that no one else bothered to use) - vlinker do a MC version to play on bikes correctly that also does GM https://www.vgatemall.com/products-detail/i-5/ )
One day when they work out how we'll be able to buy just one and it will do everything - but today there's isn't one out there - unless you go the $2000 route and even then its a lie....
the set up above (a decent app and a decent dongle) should be in the pocket of ANYONE ever starting ANY modern car or bike at ANY time.... they are that ALL that badly made - today its madness not to have it with you 24 7
.
Last edited by BOTUS; Mar 3, 2024 at 06:28 AM.
Thread Starter
Newbie
Joined: Mar 2024
Posts: 2
Likes: 0
S550
I put the car through a scan and a cylinder 3 misfire came out along with a random misfire. I switched my cyl 4 coil with my cyl 3 coil but the idle is still rough. I also noticed the exhaust was smoking while I was at a light which makes me lean towards a broken gasket but I want to hear what else it might be.
