I need an Audi genius!!!!!

Slice636

S5 3.0tfsi. Sprint blue
Hi everyone,

My car has been misfiring on start ups for a few weeks now, it will only misfire from ‘warm’ not hot/cold
It will only missfire when you hit the start button straight away. If you turn on the ignition first it won’t misfire?
The missfire disappears after the elevated revs have gone down to 6/700

I’ve changed all the plugs and coil packs too
The car isn’t showing any codes either
It can’t be fuel pressure as it won’t do it from cold
It’s an s5 3.0tfsi

Thanks
 

MuPPeT_ON_TouR

Registered User
Think you are down to injectors and or possible carbon build up not allowing valves to close fully as a cause of the misfire. Off the top of my head I'm not sure what else can cause misfire.... BUT I am no expert.

When you say it doesn't show any codes, how do you know its a misfire? Not doubting your knowledge just looking for as much info as possible for those who are more knowledgeable than myself to be able to help.

How many miles on the clock does your car have?
 

Slice636

S5 3.0tfsi. Sprint blue
Yeah I fully understand, Vcds isn’t logging any misfires but the car sounds like it’s misfiring as it sounds awful (suburb sounding) quite a few burbles and popping though exhaust if you slightly rev it and the whole car shakes and it’s only on 77k :(
 

Slice636

S5 3.0tfsi. Sprint blue
No it’s a very strange one, had it hooked up to vcds at a tuner and they couldn’t see anything obvious, fuel pressure, timing, etc the only next solution i can possibly think of is throttle body and if that’s no avail then take the supercharger off and send all the injectors for testing and carbon clean it whilst it’s off but that’s £££
 

MuPPeT_ON_TouR

Registered User
Take a punt at one of the engine carbon cleans. They are £70/80 and only take an hour. If they solve it, it will only be temporary but at least you know it's the right direction and a cheap diagnosis.

If it does nothing then I'm afraid it probably means you wasted £80 as you still couldn't rule out carbon as a cause.


I still can't get my head around no fault codes though.
 

Meemo

Registered User
Sorry I am sure you have, but have you done live cylinder logging from vcds, not just checking if it has any misfire related codes?
I ask because on a previous car I had a hesitation but no codes logged, so did a live log run and set it to log in the cylinders and recorded something like 50 misfires a minute from just one cylinder, certainly wasnt telling me any other way.
Can't remember how I got to this screen as was a good 8 years ago but I can always take a look on the laptop later if it helps.
 
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