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Discussion Starter · #1 ·
Good evening :)
I’m hoping someone can advise.
I have an 2008 s5 4.2
The car has become sluggish at wot, once it reaches 5k it struggles to hit 6k if you keep pushing it’ll eventually pass. It would then follow with an missfire on cylinder 6 which would then progress to all cylinders on bank 2 misfiring.
It’ll Rev fine in neutral and it you be gentle on the throttle it’ll some times Rev fine past 6k.
It’s had the following trying to chase the fault.
All new denso plugs and Bosch coils
All new hitachi injectors
New Bosch maf
New Pcv valve
Fuel filter and air filter.
carbon clean.
Does anyone have any ideas what could be causing this Issue ?

regards
 

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A5 B8 Coupe 3.0TDI 240HP - Manual transmission
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8 Posts
Hello Roger,
once you´ve fitted all theese new parts, I would take a look at motor mounts - It can cause misfire. Motor mounts are hydraulic with electronic solenoid valve, once they go bad(pretty common) on B8 cars, they can give faulty information to the ECU, ECU thinks that the engine vibrates way more and try to compensate it with changing fuel ratio and stuff. Hope your car will be fine :)
 

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Good evening :)
I’m hoping someone can advise.
I have an 2008 s5 4.2
The car has become sluggish at wot, once it reaches 5k it struggles to hit 6k if you keep pushing it’ll eventually pass. It would then follow with an missfire on cylinder 6 which would then progress to all cylinders on bank 2 misfiring.
It’ll Rev fine in neutral and it you be gentle on the throttle it’ll some times Rev fine past 6k.
It’s had the following trying to chase the fault.
All new denso plugs and Bosch coils
All new hitachi injectors
New Bosch maf
New Pcv valve
Fuel filter and air filter.
carbon clean.
Does anyone have any ideas what could be causing this Issue ?

regards
I have the exact same car and year with just under 100K miles with the same problem. I was told I need new coils.
 

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3,722 Posts
RogerN mate this is a strange one indeed!! PLEASE keep us informed as and when you make progress. How many miles have you on your car and do you think that this came on with cold or rain or what???? Wierd eh??
 

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Discussion Starter · #10 ·
Car is on 100k, the bank 2 igniter in ecu failed ?
The car seemed to be losing power for a while but I put it down to just me thinking that.
It then started with cylinder 6 missfire and progressively to all cylinders on bank 2.
The only thing that has happened was an rocket cover leak into cylinder 6 plug well which may have shorted out but I’d be surprised if that passed onto the ecu.
 
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