Misfire on cylinders 5 and 8

[waybar17]

Hi, I've just done the NC500 driving route covering 2,000 faultless miles in one week - absolute dream

The M5 has been parked for a week since returning and I've just gone to move it and it's reporting misfire on cylinders 5 and 8.

I cleared the faults and captured runtime data - does anyone know if this looks ok?

Ignition Timing (On Running Engine) 3.00°crank angle

Knock Signal, Cylinder 5 7.14V
Knock Signal, Cylinder 6 5.21V
Knock Signal, Cylinder 7 6.04V
Knock Signal, Cylinder 8 5.69V
Misfire, Cylinder 5: Counter 0
Misfire, Cylinder 6: Counter 0
Misfire, Cylinder 7: Counter 0
Misfire, Cylinder 8: Counter 0
Rail Pressure 2 5.01MPa
Status Of Terminal 15 (Bus Signal)On
VANOS Exhaust 2: Position (While Engine Is Running) 11.09°crank angle
VANOS Intake 2: Position (While Engine Is Running) -3.78°crank angle
Voltage,Terminal 87 15.07V

The knock signal voltage on 5 & 8 was at 12v during warm up, with 6 & 7 at 7v then when revs dropped it dropped to the above readings

Any ideas on what parts to start replacing ?


thanks

[M5Rick]

Need details of year, mileage and if car has any engine modifications, like a tune and catless pipes.

[waybar17]

2012, totally stock, 107k miles - owned for 7 years and never missed a beat

[M5Rick]

Can't add to what caused the codes but first thing clean the MAF's with CRC spray (which you've probably already done) then check clamp tightness on turbo pipes and the vacuum pipes which may have a breach after those miles and when were air filters last changed. I'd stick to the basics before going onto things like coils which I gather have been replaced at some time, HP fuel pumps can give trouble later on.
If it's running right now then use injector cleaner every time you fill up, I use Redex petrol additive to keep it running sweet with mostly Texaco 99 fuel, it's dearer but better. A lot of smaller things can lead to these codes being shown.
.

[waybar17]

Originally Posted by M5Rick

Can't add to what caused the codes but first thing clean the MAF's with CRC spray (which you've probably already done) then check clamp tightness on turbo pipes and the vacuum pipes which may have a breach after those miles and when were air filters last changed. I'd stick to the basics before going onto things like coils which I gather have been replaced at some time, HP fuel pumps can give trouble later on.
If it's running right now then use injector cleaner every time you fill up, I use Redex petrol additive to keep it running sweet with mostly Texaco 99 fuel, it's dearer but better. A lot of smaller things can lead to these codes being shown.
.

thanks, good advice, it is running fine now, but I've ordered and set of plugs and coils. I use Tesco 99 or V-Power, but never added Redex so worth a try.

[KurtsM5]

Originally Posted by M5Rick

Can't add to what caused the codes but first thing clean the MAF's with CRC spray (which you've probably already done) then check clamp tightness on turbo pipes and the vacuum pipes which may have a breach after those miles and when were air filters last changed. I'd stick to the basics before going onto things like coils which I gather have been replaced at some time, HP fuel pumps can give trouble later on.
If it's running right now then use injector cleaner every time you fill up, I use Redex petrol additive to keep it running sweet with mostly Texaco 99 fuel, it's dearer but better. A lot of smaller things can lead to these codes being shown.
.

Wait...is that 99 octane???

[M5Rick]

Originally Posted by KurtsM5

Wait...is that 99 octane???

Sure is 99 octane RON. Texaco Supreme Performance+ has not long been introduced and only a fraction of Tex stations stock it. Nearest to me is about 3 miles away but worth the trip.

[KurtsM5]

Originally Posted by M5Rick

Sure is 99 octane RON. Texaco Supreme Performance+ has not long been introduced and only a fraction of Tex stations stock it. Nearest to me is about 3 miles away but worth the trip.

You've got to be paying a fortune for it. What tune do you have?

[M5Rick]

Originally Posted by KurtsM5

You've got to be paying a fortune for it. What tune do you have?

All stock. Your premium US 93 gas is the same octane rating as the 98-99 octane RON over here and the Tex fuel is a few pence a litre above the others except for Shell v power which is even dearer than Tex, but I find V Power may have too many cleanser additives in it. RON stands for Research Octane Number.

[KurtsM5]

Gotcha.