S65 AMG misfires (not the usual)

bembo449

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well I guess by the time MSL have finished you will have some sort of final diagnosis and one way or another a smooth running motor
 
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alexanderfoti

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well I guess by the time MSL have finished you will have some sort of final diagnosis and one way or another a smooth running motor

Fingers crossed!
 
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alexanderfoti

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Update for all. I had to postpone the MSL appointment as work commitments came up last minute (happens all to often to spoil my fun!).

I had a big project going on and stopped working on the car for a bit. By chance, a guy in america messaged me on the V12 facebook group asking for my advice. He had the exact same symptoms as me (misfiring above 4900 rpm). I asked him what had been done etc.

He had a set of upgraded turbo's from the now defunct Speedriven. Unfortunately for him, they sold him the package which consisted of turbo's, larger intercoolers, and a remap, just before they closed down, so he was stuck in the water with no assistance.

He mentioned to me that speedriven told him that the wastegates may need to be adjusted on his new turbo's after installation. That had me thinking, the only thing that is seperate between the banks, that I had not checked is the turbo's!

I balanced the wastegates by applying 10 psi to the wastegate line and watching each side open. The passenger bank (with the misfires) was opening slightly later than the drivers side bank. I adjusted the nuts so they both opened at the same time and voila, problem solved!!

The misfires where caused by the higher turbo backpressure on the passenger side bank at high rpm.

So to sum up, initial low power was caused by worn TC and dodgy TC lockup valve and worn TC clutch bore in the valve body.
Then EC remap was applied
Then misfires started above 4900rpm.
I replaced:
plugs
coil packs X 2 £1000 each
ignition controller x 1 £500 each
fuel injectors x 12 £lots
O2 sensors x 2 £150

Various other bits, and it was the turbo's all this time.

Oh well! Nice to have closure and to be able to drive the car properly for the first time in 6 months, thanks everyone for their help!
 
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alexanderfoti

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Why do you assume it was back pressure that caused it? Could just as easily be excessive boost before the gate opened.....good you have fixed it.

because the turbo outlets are tied together just after the intercoolers. The boost is regulated by actuation of the boost control solenoid which takes a boost source and routes it to both turbos with a t piece.

I only had to wind the passenger side gate in one revolution,drivers side did not need adjusting.

You could conceivably end up with one turbo doing less work and one turbo doing more work and still being within the right boost numbers.
 
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Wighty

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Update for all. I had to postpone the MSL appointment as work commitments came up last minute (happens all to often to spoil my fun!).

I had a big project going on and stopped working on the car for a bit. By chance, a guy in america messaged me on the V12 facebook group asking for my advice. He had the exact same symptoms as me (misfiring above 4900 rpm). I asked him what had been done etc.

He had a set of upgraded turbo's from the now defunct Speedriven. Unfortunately for him, they sold him the package which consisted of turbo's, larger intercoolers, and a remap, just before they closed down, so he was stuck in the water with no assistance.

He mentioned to me that speedriven told him that the wastegates may need to be adjusted on his new turbo's after installation. That had me thinking, the only thing that is seperate between the banks, that I had not checked is the turbo's!

I balanced the wastegates by applying 10 psi to the wastegate line and watching each side open. The passenger bank (with the misfires) was opening slightly later than the drivers side bank. I adjusted the nuts so they both opened at the same time and voila, problem solved!!

The misfires where caused by the higher turbo backpressure on the passenger side bank at high rpm.

So to sum up, initial low power was caused by worn TC and dodgy TC lockup valve and worn TC clutch bore in the valve body.
Then EC remap was applied
Then misfires started above 4900rpm.
I replaced:
plugs
coil packs X 2 £1000 each
ignition controller x 1 £500 each
fuel injectors x 12 £lots
O2 sensors x 2 £150

Various other bits, and it was the turbo's all this time.

Oh well! Nice to have closure and to be able to drive the car properly for the first time in 6 months, thanks everyone for their help!
That's funny because I'd thought that might have been the problem :rolleyes: (glad it's all sorted )
 


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