NA 63 Misfire diagnosis for very rough hot idling
Thread Starter
Junior Member
Joined: May 2020
Posts: 59
Likes: 18
From: NYC
2004 E55, 2006 E500 wagon, 2014 E350
NA 63 Misfire diagnosis for very rough hot idling
Is anyone familiar with logging misfire data that could give a pointer or two? I'd like to try and see if I have a failing coil pack or spark plug but I think read someplace that you could only measure the secondary windings with a DMM, or some crap like that? Anyway, if someone would be gracious enough to share some knowledge on logging KPIs, I'd be very grateful. I've got a Xentry laptop, and I also have an ODB BT dongle with the torque app. I was looking through torque but I didn't really notice anything specific to plugs or coils, mostly timing, temps, AFR, MAP and MASS, speed yatta yatta yatta.
A little background: Bought the car in August but haven't really used it much; a few hundred miles tops. Cold start is real smooth, no noise or smoke, idles great. After it gets hot though, the idle gets real rough. I smoke tested it and found a bad PCV. I pulled the manifold to replace it, and while I had it out I opened it up and found a nice hole in the throttle plate. Replaced, cleaned, painted, fresh PCV and gaskets, car is still doing the same thing. Now, when you're accelerating it's fine. Pulls real strong. My brother has the same car and they are equally fast so it's hard to believe it's plugs or coils, but I'd like to rule that out.
Also, zero codes except for the rear 02s because of the headers. Could the upstream 02s cause this?
A little background: Bought the car in August but haven't really used it much; a few hundred miles tops. Cold start is real smooth, no noise or smoke, idles great. After it gets hot though, the idle gets real rough. I smoke tested it and found a bad PCV. I pulled the manifold to replace it, and while I had it out I opened it up and found a nice hole in the throttle plate. Replaced, cleaned, painted, fresh PCV and gaskets, car is still doing the same thing. Now, when you're accelerating it's fine. Pulls real strong. My brother has the same car and they are equally fast so it's hard to believe it's plugs or coils, but I'd like to rule that out.
Also, zero codes except for the rear 02s because of the headers. Could the upstream 02s cause this?
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Joined: Jul 2014
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2005 e55 AMG
Monitor your pids for the O-2 sensors and see what your fuel trims are "warm" and then "hot" and compare.
Remember the rear O-2 sensors tell the ECU weather or not the front O-2 sensors,and cats, are doing there job correctly so defeating the rears or shutting them off does not help the cause at all when a problem comes up in a fuel related issue. I have seen a sticky/dirty injector cause this issue and found it from injector flow testing.
Remember the rear O-2 sensors tell the ECU weather or not the front O-2 sensors,and cats, are doing there job correctly so defeating the rears or shutting them off does not help the cause at all when a problem comes up in a fuel related issue. I have seen a sticky/dirty injector cause this issue and found it from injector flow testing.
Thread Starter
Junior Member
Joined: May 2020
Posts: 59
Likes: 18
From: NYC
2004 E55, 2006 E500 wagon, 2014 E350
@trigital I'll check that smooth running setting and see what is shows.
@SICAMG I replaced all the injectors immediately after I saw they were the originals with 174K miles on them (scary). I also installed 200 cell cats onto the LTH and rolled the tune back to stock because the Eurocharged tune had a lot of monitors coded out and it wouldn't pass NYS inspection. It did pass after the work, but the rear 02 codes return within about 100 miles of driving. I had to use 02 extenders to keep the CEL longer in order to pass inspection BTW. I'll try and log what you suggested.
@SICAMG I replaced all the injectors immediately after I saw they were the originals with 174K miles on them (scary). I also installed 200 cell cats onto the LTH and rolled the tune back to stock because the Eurocharged tune had a lot of monitors coded out and it wouldn't pass NYS inspection. It did pass after the work, but the rear 02 codes return within about 100 miles of driving. I had to use 02 extenders to keep the CEL longer in order to pass inspection BTW. I'll try and log what you suggested.
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Joined: Oct 2023
Posts: 170
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Is anyone familiar with logging misfire data that could give a pointer or two? I'd like to try and see if I have a failing coil pack or spark plug but I think read someplace that you could only measure the secondary windings with a DMM, or some crap like that? Anyway, if someone would be gracious enough to share some knowledge on logging KPIs, I'd be very grateful. I've got a Xentry laptop, and I also have an ODB BT dongle with the torque app. I was looking through torque but I didn't really notice anything specific to plugs or coils, mostly timing, temps, AFR, MAP and MASS, speed yatta yatta yatta.
A little background: Bought the car in August but haven't really used it much; a few hundred miles tops. Cold start is real smooth, no noise or smoke, idles great. After it gets hot though, the idle gets real rough. I smoke tested it and found a bad PCV. I pulled the manifold to replace it, and while I had it out I opened it up and found a nice hole in the throttle plate. Replaced, cleaned, painted, fresh PCV and gaskets, car is still doing the same thing. Now, when you're accelerating it's fine. Pulls real strong. My brother has the same car and they are equally fast so it's hard to believe it's plugs or coils, but I'd like to rule that out.
Also, zero codes except for the rear 02s because of the headers. Could the upstream 02s cause this?
A little background: Bought the car in August but haven't really used it much; a few hundred miles tops. Cold start is real smooth, no noise or smoke, idles great. After it gets hot though, the idle gets real rough. I smoke tested it and found a bad PCV. I pulled the manifold to replace it, and while I had it out I opened it up and found a nice hole in the throttle plate. Replaced, cleaned, painted, fresh PCV and gaskets, car is still doing the same thing. Now, when you're accelerating it's fine. Pulls real strong. My brother has the same car and they are equally fast so it's hard to believe it's plugs or coils, but I'd like to rule that out.
Also, zero codes except for the rear 02s because of the headers. Could the upstream 02s cause this?
