M-Class (W166) Produced 2012-2015

2012 ML350 Rough Cold Start

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Old Nov 4, 2023 | 11:39 PM
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korea348's Avatar
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2012 ML350 W166
2012 ML350 Rough Cold Start

Hey everyone! Hoping someone more knowledgeable than I can help.

I recently returned from a week trip out of town and when I went to start my 2012 w166 ML350 (gasoline with 130k miles), it had a rough start and the car shook as it idled. It's never done this before. I turned the car off and immediately started it again to find it started without issue and idled smoothly.

No check engine light... Is this something I need to investigate more thoroughly? Is it worth replacing the spark plugs prophylactically (2nd owner, CPO, owned since 50k miles, unknown if they've been replaced)?

TIA
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Old Nov 5, 2023 | 03:12 PM
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ML400 - 128i - Atlas VR6
Is it possible to post a vid of the next cold start?
Have the timing chain tensioners been replaced and check valves installed from the TSB? I am sure your engine is in the affected range.
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Old Nov 6, 2023 | 02:28 PM
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W204 C63 Coupe, W166 ML350 BlueTEC, 928GT, Taycan GTS Sport Turismo, C5 Z06 & IS300 race cars
Originally Posted by korea348
Hey everyone! Hoping someone more knowledgeable than I can help.

I recently returned from a week trip out of town and when I went to start my 2012 w166 ML350 (gasoline with 130k miles), it had a rough start and the car shook as it idled. It's never done this before. I turned the car off and immediately started it again to find it started without issue and idled smoothly.

No check engine light... Is this something I need to investigate more thoroughly? Is it worth replacing the spark plugs prophylactically (2nd owner, CPO, owned since 50k miles, unknown if they've been replaced)?

TIA
Get yourself an OBD2 code reader and see if there are any stored codes in the ECU. Ignore comments of the "disastrous" variety at least until you have more data and/or have eliminated the myriad of little things that are 1000 times more likely to cause a (temporary) misfire.

Originally Posted by Gray_Panther
Is it possible to post a vid of the next cold start?
Have the timing chain tensioners been replaced and check valves installed from the TSB? I am sure your engine is in the affected range.
Most of the time a headache is just a headache (because you may have a cold), not a result of a brain tumor which is the equivalent of what you're suggesting here. Based on what evidence exactly did you come to the conclusion that the timing chain tensioners are the likely culprit?
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Old Nov 6, 2023 | 03:27 PM
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Originally Posted by Diabolis
Get yourself an OBD2 code reader and see if there are any stored codes in the ECU. Ignore comments of the "disastrous" variety at least until you have more data and/or have eliminated the myriad of little things that are 1000 times more likely to cause a (temporary) misfire.



Most of the time a headache is just a headache (because you may have a cold), not a result of a brain tumor which is the equivalent of what you're suggesting here. Based on what evidence exactly did you come to the conclusion that the timing chain tensioners are the likely culprit?
Savage man. Very brutal.
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Old Nov 6, 2023 | 05:41 PM
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2008 E350, 2012 ML350, 2014 E350, 2015 ML350
Originally Posted by korea348
... I went to start my 2012 w166 ML350 (gasoline with 130k miles),..

No check engine light... ... Is it worth replacing the spark plugs prophylactically (2nd owner, CPO, owned since 50k miles, unknown if they've been replaced)?
Very confusing message. If I understood correctly, you bought the car @50K miles, and it is now @130K miles and you do NOT know if the spark plugs have been changed? They were due at 60K miles the first service, and again @120K miles, i.e. both within your ownership period. If you have not done spark plugs on this car for that long, would you mind detailing what else have you skipped?


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