E63 5.5 TT Misfire

[E55BOF]

Oh Sh!t! I've only had it for ten days...

The car is a 2012 E63 5.5 TT with Performance Package. Under full throttle it pulls as normal to the red line, then starts misfiring and the EML comes on.

It first did it last night; I changed the mode from Comfort to Sport+ on the move, then gave it all the beans joining the motorway. I lifted off at once, and found it would run on very small throttle openings, but any more than that and it would misfire. Once home, it idled roughly. I switched it off, then on again, and the EML extinguished.

I thought at first it might be changing the mode on the move that was the cause, but there's nothing in the handbook that I can find warning against doing that.

Started up this morning in Comfort, and left it there; no EML once it had fired up. Started and ran entirely as normal, until I gave it full power in the same situation, still in Comfort mode. It pulled as normal to the red line, then misfired and the EML came on. (I didn't/don't have the balls to keep my foot down and see what happened). This time, the restart is entirely normal, as before, but the EML light now stays on all the time. This time, it appears to be running fine on medium throttle openings without misfiring.

Does anybody have any idea what it's likely to be?

 

[ashenfie]

You need to get the codes read, even with no EML there should be code stored.

 

[st13phil]

Sorry to hear that

It won't be anything to do with changing the engine mode on the move as you can do that ad nauseum.

As with all faults like that, speculation is unlikely to be accurate: you need to get it on STAR and get the codes read.

 

[st13phil]

Any news on the cause?

 

[E55BOF]

The car drives perfectly normally (still with the EML on; stored code now, I presume), i.e. goes like a scalded cat on steroids with its ar5e on fire, until it gets up near the red line, when pronounced, ragged misfiring occurs. If (as I presume) there's a rev limiter, and it operates by restricting the fuel supply, off the top of my head a fault there would seem to fit the symptoms, but that's just my best guess.

It's going in to Terry Gates on Friday; he also thinks it's most likely to be a fuel problem. I'll leave it to him to find out.

 

[st13phil]

I guess you'll find out on Friday then!

FWIW, hitting the rev limiter on the 5.5 Biturbo feels like hitting a brick wall. It doesn't go soft and ragged, it just cuts dead.

 

[Deleted member 37751]

Good luck for tomorrow Dennis, no finer mechanic to have on the job than Terry.

 

[E55BOF]

It went in yesterday (Terry was up to his ears on Friday). The EML was still on, but STAR revealed only four stored faults, all very old (around 22K miles; the car's done four times that) - two cylinder misfires, a 'charge cooling insufficient' and one other. Nothing conclusive, no indication of possible cause, so Terry cleared them and I took the car to the motorway to give it some beans and see what came up fresh.

"Warp Factor 9, Mr. Sulu", and.....nothing. No EML, nothing. It pulls to the red line, changes up, and keeps on pulling entirely normally (and boy, does it ever pull; Chinese friend's name time again...) until I chicken out.

Bugger! I hate intermittent faults. Modern cars have so much electronic wizardry, perhaps it was a one-off glitch which will never recur (touch wood). Just in case, though, I've ordered an iCarsoft, and I'll keep it in the car, so if it happens again, I can get an immediate readout.

 

[st13phil]

Thanks for the update. As you say, intermittent faults are a royal PITA, but with luck it'll never happen again.

 

[bluestreak]

Fingers cross indeed Dennis. Hope it is something simple. If it persists reading codes might not be enough.

I had persistent misfire, which turned out to be a faulty spark plug. Other common fault could be ignition coil. If misfire becomes more "reliable" then may be it is worth looking into those two thing for affected cylinders.

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[E55BOF]

A persistent misfire would be easy to diagnose. The problem is, the problem isn't persistent... All I can do is crack on unless or until it recurs, and deal with it then.

 

[C43AMG]

I think what could have happened is the previous owner might never have used manual and took it to the Red Line Just went into Shock Mode and now it's used to it everything is okay

 

[bluestreak]

I think what could have happened is the previous owner might never have used manual and took it to the Red Line Just went into Shock Mode and now it's used to it everything is okay

I didn't realise "shock mode" was a thing [emoji53]

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[E55BOF]

I like the idea of Shock Mode, but I'm not sure I believe it...

 

[Pondman]

I didn't realise "shock mode" was a thing

or should that be "shock and awe mode"

glad to hear it seems to have resolved itself.........

 

[Cyclone1]

If it comes back then plugs / coils. Out of interest was cylinder 5 one of the two affected in the fault codes?

 

[Cyclone1]

Repost

 

[E55BOF]

If it comes back then plugs / coils. Out of interest was cylinder 5 one of the two affected in the fault codes?

Yes it was; pots 5 and 6. You obviously have an inkling; do please share it.

If/when it does recur, will the iCarsoft MB II be able to pinpoint the cause of the misfiring if it is plugs or coils, or will it just record the misfire/s?

 

[bluestreak]

crankshaft position sensor reports misfires, but not the cause unfortunately. Other sensors may or may not corroborate a cause but more often then not you need to try to eliminate these things:

- spark plugs (two per pot)
- ignition coil
- injectors
- compression
- crankshaft position sensor (unlikely if you have specific cylinder misfire)

positive effect of intermittent misfire is low probability of cylinder damage, which causes compression issues. Most likely the cause is one of first three.

 

[E55BOF]

Well, Terry Gates' first thought was a fuel problem, and in my experience neither plugs nor coils, if faulty, start working again spontaneously. Given the regime the problem occurred in -up near the red line - I still wonder if it was the rev limiter playing up a little. I'll just have to wait and see, and hope it doesn't recur. So far so good...