Diagnosis of my lack of kick over 5000 rpm

[Dave_M]

started this as a separate thread as the other one's got a bit cluttered!

My VAG COM turned up end of last week (only 3 days after ordering it from Ross Tech in the US), so hooked it up to the car yesterday.

First off, managed to reprogram to get rid of the annoying need to press the unlock button twice to unlock all doors, and also now have the RS4 startup screen on the sat nav.

Then ran the Output tests. I could see (and hear) the inlet manifold flaps operating. I didn't have much time so didn't remove the airbox snorkel - however, I couldn't hear anything happening. I'm assuming I should hear the flap move and also the vacuum airflow noise - as for the intake flaps - so I'm guessing the airbox power flap has jammed. When I looked in the top of the airbox before I couldn't see the flap (used a torch) so my guess is it's jammed shut - hence the lack of kick at high revs and also no "hard" induction noise.

Can someone provide an idiot's guide to removing the airbox - I understand it can be done without removing the bumper.

Cheers
Dave

[neckarsulm]

Mine was stuck open, during the output test I could hear something happening and assumed it was OK.
When I eventually checked (you can see it if you use or torch, you can just feel it too if your hands aren't too big) it was just moving a few degrees instead of 90 degrees.

A rough guide to airbox removal is as follows, will do a proper guide later in the week - there may be minor errors in this so beware it is at your own risk;

You need Philips screw driver, T30 Torx driver (longer the better), flat blade screwdriver, Torx driver to undo coil loom (T25 I think)

Undo 2 screws on slam panel that retain front section of snorkel.
Pull off the snorkel piece from top of airbox and remove front bit of snorkel.
Undo 2 screws that retain air box cover and unclip a pipe that rests on top of it
Undo hoseclip that retains intake boot to MAF/airbox lid
Carefully slide airbox lid upwards, when free remove it from intake boot (may be a difficult so carefully use a wide flat blade screw driver to loosen the boot's seal on lid)
Remove filter element
Unclip loom that runs across the top of the air box base from airbox base using flat blade screwdriver
Pop out the plastic dowel pin that locates the air box base into the inner wing, make a note how it and the other plastic bits go together

At this point if you can undo the 3 T30 Torx bolts that hold the headlight in (2 visible, outer one well hidden)and move it forward that will make life a lot easier - I only could undo the inner 2 bolts which allowed the headlamp to move a bit and made what would have been an impossible job a bit easier. If you have a long T30 tool then all 3 should come out

If not you will have to fumble around behind the headlight to unclip the vac pipe off the power flap valve
You will also need to undo the 2 small Torx screws that locate the coil loom onto the rocker cover and unplug it from coils to make enough clearance to get the airbox out

Once everything has been detached from the air box base give it a firm pull upwards to release it from the chassis leg, be careful not to damage the power flap valve which sticks out and virtually touches the back of the headlamp.

With the headlamp out it should just lift out, with it in you will have to carefully try and get it out by trying a few different angles. If you found that hard, getting it back in is even harder!

[lengster1]

Be gratefull of a step by step runthrough on how to get the rs4 screen on the navvy and one click opening aswell

[silverRS4]

Dave M - you didn't hear anything at all when you ran the power flap test (Intake Air Switch over valve 'Output test')? I can't imagine it would be difficult to hear even with the snorkel on. You are probably right about the flap not operating. The vacuum line going to it may be pinched completely, rendering the solenoid and flap completely inactive. There have been instances of that...the headlight assembly or something had crushed the vacuum line (implying that, at the factory, the headlights are installed after the vacuum hoses, which makes sense). But before you worry too much, do the test again with a torch shining in the airbox with the snorkel off just to make sure its not moving.

[Dave_M]

Neckarsulm - thanks very much for that. Hopefully I'll get time to have a proper look at it next sunday.

Lengster1 - I'll post up what you need to change for these 2 - assume you have VAG COM - or know someone who does?

SilverRS4 - I plan on checking with a torch before I pull the whole airbox out - but given the symptoms I've got, the power flap looks like the culprit.

Cheers
Dave

[lengster1]

Thanks Dave m,yep i have vagcom

[Dave_M]

OK, have the day off today so thought I'd tackle this. Checked again with VAG COM with the snorkel removed - no movement at all from the valve.

I've got the cover off the airbox and the top two bolts on the headlight removed - question - how do I remove the vacuum pipe from the actuator? You mention "unclip vac pipe" - but I can't see how it clips onto the actuator. Does the rubber pipe pull off completely, if not what should unclip and how? Don't want to break anything as I need the car tomorrow!

Cheers
Dave

[neckarsulm]

..from what I recall the pipe is an interference fit so just pulls off, there is no clip, sorry for the ambiguity.
As ever it's prob quite tight so be careful no to pull too hard onto the valve.
I think I managed to pull the pipe off before I undid the airbox at all, easier with airbox secured as you are pulling against something fixed.

Sorry I haven't done full write-up, not had the time.

[Dave_M]

Thanks - got the pipe off now - it was an interference fit.

Next problem - how do the clips release where the loom connects to the coils? I'd assumed you need to press down on the tab (furthers bit of the coil from the spark plug end) and the loom plug would then pull out. None of the tabs seemed willing to move at all - and a bit more pressure has just resulted in me breaking one of the tabs off .

Cheers
Dave

[neckarsulm]

coil plugs are fun!
press down on the tab and push the plug towards the coil, this should then click, keep pressure on tab and then pull the plug off the coil
you can apply some pressure to the tab with a suitable flat blade screwdriver but as you have found out they do break quite easily

[Dave_M]

Cheers

I'll have to have another try on another day - ran out of time yesterday so ended up putting it back together again!

Dave

[RS6chris!]

Reading this "power flap" isue with intrest....i sometimes dont know if ive lost the kick at 5 rpm or not...seems hit and miss??

Anyway...why cant the flap just be removed?? Surely it wont make a difference and the airbox would get maximum air all the time especially above 5 k??

Yes?...No?.

[neckarsulm]

I asked that in the original thread and SilverRS4 pointed out that the air from the front is heat soaked unless the car is moving at a good speed so it only open when air flow is sufficient to overcome this.
Just ask yourself would quattro GmbH do this if it didn't have some benefit?

[ArthurPE]

....
Just ask yourself would quattro GmbH do this if it didn't have some benefit?

you mean you ain't smarter than the 1/2 dozen PhD's who designed the airbox system?

[Dave_M]

RS4414

Mine started out like that - sometimes I got the kick, sometimes not. Then it stopped altogether!

Dave