Help..S3 8P BHZ hesitation at 3000-3500rpm

Davill9

Member
Hi
Sorry everyone if I have posted wrong or in the wrong place, this is my first ever post on the internet ever....

I have a 2008 S3 with BHZ engine and have had a strange hesitation since buying it back at the end of January this year.

it is not really noticeable in most gears but is noticeable in 5th and mainly 6th gear and only if you are just maintaining speed or very very gradually accelerating Ie using about a cm of the accelerator pedal.
It starts around 3000 rpm and stops at about 3600 rpm.
If you accelerate using even quarter of the pedal, it drives fine and if you are driving harder , it is flawless.
It is only when holding the car in say 6th gear at around 70-80mph which is around the above revs or in 5th doing the same revs.

it is like a misfire but just a single one every few seconds, like a blip or hesitation for a split second and then another one or two a send or two later ongoing at just this Rev position and with hardly any load / accelerator pedal. Just like maintaining the speed or very gradually increasing speed.
I have changed
Coils for r8 ecs ones
Plugs for ngk71x
Genuine pcv and top/bottom hoses/gasket
Genuine n80 valve
Peirberg d/v
Sealed exhaust cat to rear hole and re fitted a standard rear section with new genuine clamp (was a straight pipe when bought)

I have had no change at all although I did get a coil down with cyl4 misfire code the first week of owning as the car had eBay special coils fitted so they went in the bin and fitted ecs ones.
The new pcv did stop the very slight needle movement on idle but all the above has made no difference to the car whatsoever.
It also drives perfectly if you use more than 1/4 of accelerator pedal in all/any gears

I could continue replacing parts until I have effectively built a new s3 but I was hoping to have left that one to Audi when it was first made.
Unlikely but want to check compression as it is only thing not yet checked really but don’t know how to disconnect the hpfp from sending fuel in as it is cam driven and can’t just be unplugged. Can disconnect in tank plug but it would surely still suck fuel without thaw in tank pump wiring connected ?

many ideas on where to look/ check next. ?
Thanks anyone in advance.
 

Davill9

Member
If this helps, a friend scanned the car a few weeks ago and no faults but found these in the stored soft codes or something

but could have been from me testing/unplugging stuff or just old codes
 

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Davill9

Member
And then I scanned car and I get no codes either but 2 pending codes after about a week gap every time

Oh and all faults- soft and historical were cleared by my mate a few weeks back
 

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Davill9

Member
And I get the P0420 code after most drives longer than 10mins nearly every time. Still not a code though- just always pending and no lights on the dash ever From the beginning and even now still no dash lights.
 

prt57

Registered User
Is your car mapped or still running standard software?
Depending on mileage it may benefit from walnut blasting the inlet valves as they can get really choked up. At the same time, have the injectors flow tested as you may have a weak one which could cause this fault. You don’t want a weak injector as that can lead to piston problems.
 

nluk100

Registered User
Have you changed the fuel filter at all? Check the old one for any contamination. Also, have you got an aftermarket downpipe on it?
 

Davill9

Member
Is your car mapped or still running standard software?
Depending on mileage it may benefit from walnut blasting the inlet valves as they can get really choked up. At the same time, have the injectors flow tested as you may have a weak one which could cause this fault. You don’t want a weak injector as that can lead to piston problems.
Hi
Sorry for long reply, I am just learning to use a forum
I assumed I got notified when I had responses but worked out how to find threads now just about.
Yes the car is mapped, by Rick at unicorn and is stage 1. It has low @310hp and high 332.4hp (manual trans)
Valves and injectors are last thing I will be addressing at some point soon as routine if this is fixed before even.
Mir has done about 142,000 miles so quite high or the highest I have ever owned in 20 years or so
- apart from maybe an old nova that was on 60,000 but they never made dashes with the extra 1 to reach - they just went back to 0 miles
I have now got OBDeleven so have been checking lots of things in live data too as well as a smoke test I did the other day and found about 15 intake leaks which are being addressed as we speak.
the dipstick has already made a massive difference at idle and driving smoothness with the revised version that actually seals , it no longer chugs like a diesel
Thanks for the response btw, really appreciated mate.
 

Davill9

Member
Have you changed the fuel filter at all? Check the old one for any contamination. Also, have you got an aftermarket downpipe on it?
Hi
Sorry for long reply, I am just learning to use a forum
I assumed I got notified when I had responses but worked out how to find threads now just about !
Yes the fuel filter has been changed and genuine from TPS.
I did do the usual check when I removed, age was about half the car’s life and was clean on outlet side and black on the inlet side so was well in need of doing.
Car has standard downpipe fitted still but going back to unicorn to get stage 2+ once I have got the car running absolutely 100% and that will include sports/de cat and new lambda 1 at same time.
 
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