Rough Idle After Spark Plug Change
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Joined: May 2016
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GL550 X166
Rough Idle After Spark Plug Change
All,
Not sure who has any ideas or have dealt with a similar issue. But I decided to do my spark plugs early at 50K miles. The car have ran perfect and now its starting to have a very slight rough idle randomly during stops at redlights. This does not happen all the time, but enough for me to notice. I replaced the spark plugs with the bosch oe plugs. Because of this issue, I went ahead and replaced them again using the factory Mercedes Benz plugs. I also changed out the coil connectors and cleaned all air filters, map sensors, etc. I checked and do not see any vacuum hoses lose or anything like that. I even tried using a fuel injector/stabilizer in the gas. At this point, I only know to replace the ignition coils.
2013 GL550
Thanks in advance for any input.
Not sure who has any ideas or have dealt with a similar issue. But I decided to do my spark plugs early at 50K miles. The car have ran perfect and now its starting to have a very slight rough idle randomly during stops at redlights. This does not happen all the time, but enough for me to notice. I replaced the spark plugs with the bosch oe plugs. Because of this issue, I went ahead and replaced them again using the factory Mercedes Benz plugs. I also changed out the coil connectors and cleaned all air filters, map sensors, etc. I checked and do not see any vacuum hoses lose or anything like that. I even tried using a fuel injector/stabilizer in the gas. At this point, I only know to replace the ignition coils.
2013 GL550
Thanks in advance for any input.
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Joined: Sep 2009
Posts: 97
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18 Model X, 13 GL350, 13 Odyssey, 07 530i
If you have a ODB2 scanner, it would probably say which cylinder is misfiring. Most likely 1) the wire to cylinder coil is not plugged in all the way, 2) the new coil is bad, or 3) coil wasn't plugged in all the way. If you have the old coils, start swapping one at a time and see which one is bad. I guess ODB2 scanner will have a record of which cylinder(s) misfired (even if it did temporarily).
Good luck!
Good luck!
Thread Starter
Newbie
Joined: May 2016
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GL550 X166
Hey, thanks for the help. I will try to use a obd scanner today. I installed new connectors onto the coils to the spark plugs. So I’m hoping that’s okay. May it is an iginition coil or the wires clipping up to it. But will the obd scanner show a misfire even if I do not have an engine check light?
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From: Chicago burbs
2015 S550
Hey, thanks for the help. I will try to use a obd scanner today. I installed new connectors onto the coils to the spark plugs. So I’m hoping that’s okay. May it is an iginition coil or the wires clipping up to it. But will the obd scanner show a misfire even if I do not have an engine check light?
Thread Starter
Newbie
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GL550 X166
Thanks for the reply man. I will try to look at the coils. It’s just odd that the coils would just act up. The connections I thought were okay. I just don’t want to go Mercedes and have them charge me 1000$ for diagnostics.
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From: Chicago burbs
2015 S550
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Thread Starter
Newbie
Joined: May 2016
Posts: 6
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GL550 X166
All,
Just an update. I took the car to a Mercedes autoshop. They ran all tests, smoke vacuum tests, compression test, electrical test, injector test, spark test and everything came back perfect. We ended up replacing the spark plugs again(3rd time) and a whole new set of coils w/ connectors. Currently, it still does it randomly every few redlights. I am just puzzled at this point. Its just very annoying, its a very slight rough idle.
Just an update. I took the car to a Mercedes autoshop. They ran all tests, smoke vacuum tests, compression test, electrical test, injector test, spark test and everything came back perfect. We ended up replacing the spark plugs again(3rd time) and a whole new set of coils w/ connectors. Currently, it still does it randomly every few redlights. I am just puzzled at this point. Its just very annoying, its a very slight rough idle.
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