Rough Idling and driving Just appear out of no where
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Junior Member
Joined: Jul 2017
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2017 GLS550 in BLACK
Rough Idling and driving Just appear out of no where
Hello everyone-
I was wondering if you all can help me. I have a 2017 GLS550. Single owner and bought it new 2016. The vehicle has been driving excellently. All maintenance have been done on it and up to date. Drove to work one day and at a stop sign, the engine light came on and it started to run REALLY rough. Drove it back from and had AAA tow it to the dealer for diagnostic. I was doing research, and it says this model year were known to have failed/bad coils. What is everyone's thoughts on this?
I was wondering if you all can help me. I have a 2017 GLS550. Single owner and bought it new 2016. The vehicle has been driving excellently. All maintenance have been done on it and up to date. Drove to work one day and at a stop sign, the engine light came on and it started to run REALLY rough. Drove it back from and had AAA tow it to the dealer for diagnostic. I was doing research, and it says this model year were known to have failed/bad coils. What is everyone's thoughts on this?
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Joined: Oct 2019
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From: Colorado
G550
Without an OBD scanner to pull the error codes, it's entirely diagnosis guesswork. The dealer will call in a couple days with a report and prognosis. Hope it's neither serious nor expensive to repair.
MBWorld Fanatic!
Joined: Jun 2021
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From: New Hampsha
'17 GLS450, '14 GLK250, Grandpa's Roadster
Our GLS450 once did something similar. I recall there was a generic misfire code stored. Turning it off and restarting it cleared the problem. It's never done it since. I called the dealer and they said something like "sometimes it happens..."
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From: In my garage
E55, GLS450, GL63, GLE350
Yes, I'm replacing all of mine this weekend. Wife had one that was on the way out, mind you just one. The shop wanted to charge her over $1k to replace one. I ordered 8 of them for around $300 and they are the insulated ones.
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From: Baltimore County, MD
'13 s212 63 p30. '06 LX470
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2015 S550, 2017 GLS450
Bad coil most likely. I hate replacing the spark plug boot with every spark plug change so I just replace the ignition coils with every spark plug service using the FCP Euro Delphi/NGK kit.
Last time I did an ignition service at around 54K miles, the spark plugs looked amazing. It’s about 120K miles so time for another service but I decided to let it run longer given just how amazing the plugs looked at my first swap out.
My experience with bad ignition coils is that it starts with intermittent misfires that come and go. So the ignition coils is the most likely culprit. It’s very useful to pull the CEL code. It gives you the cylinder number of the misfire as well although if it’s a misfire, you should replace all the coils. While you’re at it, you might as well swap the spark plugs. They are super cheap and you’ve already done 80 percent of the work.
Last time I did an ignition service at around 54K miles, the spark plugs looked amazing. It’s about 120K miles so time for another service but I decided to let it run longer given just how amazing the plugs looked at my first swap out.
My experience with bad ignition coils is that it starts with intermittent misfires that come and go. So the ignition coils is the most likely culprit. It’s very useful to pull the CEL code. It gives you the cylinder number of the misfire as well although if it’s a misfire, you should replace all the coils. While you’re at it, you might as well swap the spark plugs. They are super cheap and you’ve already done 80 percent of the work.
Last edited by bkdc; May 6, 2025 at 10:44 AM.
