2008 cl550 persistent misfire on cylinder 8 at low rpm
Junior Member
Joined: Apr 2019
Posts: 45
Likes: 1
'03 CL55
Have you replaced the injectors ? I swapped mine around and it acted the same. I replaced them anyway along with all the other stuff. How about the 02's ? I swapped mine, no change and yes, I replaced them anyway. Maybe a cat is beginning to fail ?
Thread Starter
Junior Member
Joined: Aug 2015
Posts: 56
Likes: 7
2008 cl550
Disconnected o2 sensors. Same thing.
If i unplug the fuel injector for #8 or the ignition coil, it misfires immediately (does not wait 30 sec). Stands to reason the spark plug and ignition coil are working fine.
If i unplug the fuel injector for #8 or the ignition coil, it misfires immediately (does not wait 30 sec). Stands to reason the spark plug and ignition coil are working fine.
Junior Member
Joined: Apr 2019
Posts: 45
Likes: 1
'03 CL55
I agree on replacing one part at a time, I would have done the same except the price of the parts in Canada, if you can find them, is double what is in the US (even after $ correction) so I get them shipped from our great southern neighbors. Shipping one thing at a time becomes expensive so I just did it all at the same time and with 200,000K on the car I figured it was due.
Hope you get it figured out soon. Curious to find out what the gremlin is.
You mentioned you checked and swapped plugs. How were the gaps and color?
Hope you get it figured out soon. Curious to find out what the gremlin is.
You mentioned you checked and swapped plugs. How were the gaps and color?
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Senior Member
Joined: May 2021
Posts: 251
Likes: 73
From: North of Houston, Texas
2013 CL 63, 2002 E 55, 04 Jaguar XJ8, 66 Jaguar XKE
It is the time that strikes me as the dominant clue. There is something that is being triggered at 30 - 40 seconds that is causing your misfire on #8. Somewhere there is a map of what the engine does when it starts and runs initially. Run this profile, turn this on, turn that off all based upon sensor feedback and run time.
BenzNinja may know but I don't know how to ask him. Otherwise I would spend some time (not that you haven't spent time already) finding that operating map/profile. Again, I know the frustration (felt it on a Jag I mentioned). We are wishing you the best.
BenzNinja may know but I don't know how to ask him. Otherwise I would spend some time (not that you haven't spent time already) finding that operating map/profile. Again, I know the frustration (felt it on a Jag I mentioned). We are wishing you the best.
Senior Member
Joined: May 2021
Posts: 251
Likes: 73
From: North of Houston, Texas
2013 CL 63, 2002 E 55, 04 Jaguar XJ8, 66 Jaguar XKE
Yes, it has a discussion regarding adaptation of the control unit after changes to some components and after misfire events.
I think the big thing is getting your machine on a Star system to see what it might say. I have two MBz and signed up for BenzNinja's program. Having that tool is invaluable, especially for what you are going through.
I know you are loath at this point to spend any more money but maybe someone around you has a system?
I think the big thing is getting your machine on a Star system to see what it might say. I have two MBz and signed up for BenzNinja's program. Having that tool is invaluable, especially for what you are going through.
I know you are loath at this point to spend any more money but maybe someone around you has a system?
Thread Starter
Junior Member
Joined: Aug 2015
Posts: 56
Likes: 7
2008 cl550
Some updates: New shop says compression is perfect, spark is perfect, fuel is perfect. No computer errors except for misfire on cylinder #8. OK. So now, we're all in agreement.
Next step is a leakdown test and pressure profile for cylinder #8. Should complete by the weekend.
Next step is a leakdown test and pressure profile for cylinder #8. Should complete by the weekend.
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Joined: Feb 2012
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From: Phoenix
222 S-65
OP monitoring intake vacuum as it misfires will speak of whether or not a weak cylinder is pumping air as it should.
Cam lobes healthy and happy?
Misfire only at idle means it has lots of time (relatively) compared with a misfire at 3000 rpms.
Plugging into XENTRY will be a worthwhile endeavor. Clearly you are handy with the car. Having the real MB system with a BenzNinja membership is money well spent.
Cam lobes healthy and happy?
Misfire only at idle means it has lots of time (relatively) compared with a misfire at 3000 rpms.
Plugging into XENTRY will be a worthwhile endeavor. Clearly you are handy with the car. Having the real MB system with a BenzNinja membership is money well spent.
Thread Starter
Junior Member
Joined: Aug 2015
Posts: 56
Likes: 7
2008 cl550
Well. . good news. . shoutout to Import Auto in Logan, Utah for finally fixing!
After verifying that all the hardware is in order . . . . . (perfect pressure waves, etc.). . . . .
I'm sure I'm saying this wrong, and I don't think they totally understand either, but it there are adaptations in the ECU that learn timing imperfections in every cylinder. For one reason or another, these "adaptations" can get off. Perhaps someone changed the ECU in the past without resetting these. Anyway, the misfire has totally gone away (according to them, and not yet verified by me), after resetting these adaptations. The ECU should still monitor and learn over time and shouldn't have any more problems.
Here's to hoping!
After verifying that all the hardware is in order . . . . . (perfect pressure waves, etc.). . . . .
I'm sure I'm saying this wrong, and I don't think they totally understand either, but it there are adaptations in the ECU that learn timing imperfections in every cylinder. For one reason or another, these "adaptations" can get off. Perhaps someone changed the ECU in the past without resetting these. Anyway, the misfire has totally gone away (according to them, and not yet verified by me), after resetting these adaptations. The ECU should still monitor and learn over time and shouldn't have any more problems.
Here's to hoping!
Thread Starter
Junior Member
Joined: Aug 2015
Posts: 56
Likes: 7
2008 cl550
So. . likely, the engine wasn't really "misfiring" per se, but because the timing of the ignition in cylinder 8 was too far off from where the ECU expected it to be, the ECU flags a misfire. . . . this is really at the millisecond level.
Thread Starter
Junior Member
Joined: Aug 2015
Posts: 56
Likes: 7
2008 cl550
No. . just Mercedes STAR software has the option somewhere to analyze/reset. It has to do with individually calibrating every cylinder.
Last edited by protonspring; Oct 21, 2023 at 01:39 AM.
