Airbox power flap, VCDS and main dealer problems.

[aidanjaye]

Any one gonna try it then??????????


Lol.

Tried today and it doesn't move when revs get to 5500 (with car stationary). Thought the flap may have been seized but with car off, flap can be easily moved by hand.

[neckarsulm]

Tried today and it doesn't move when revs get to 5500 (with car stationary). Thought the flap may have been seized but with car off, flap can be easily moved by hand.

Could still be knackered if it's not seized though

[Terry1948]

I think I may also have siezed flap issues on the car that is. Ordered VCDS on Friday and it came this morning will be tapping into superior knowledge of you other guys when I need help if that is okay. Worked out that it would pay for itself with just going abroad a few times.

[ArthurPE]

Why not rev to 5k when stationary??? Less load.

less load (or no load) is the problem...
the engine is generating significant power/energy, with no load, it has to be absorbed somewhere, usually the crank, it flexes...
it can't be dissipated thru the wheels and driving the car forward...

F = ma, m being the engine mass, which is being accelerated...
the force must go somewhere, Newton, for every force, an opposite and equal reaction, in this case the block/crank/etc.

BMW specifically issues a warning not to do it in the e46 M3, the crank so long, and rev's so high, coupled with rod bearing issues, lead to bad thins happening...

[RS6chris!]

Had a good poke about in the airbox tonight (just realised that sounds dodgy!!!)

anyway it looks like there is some sort of solenoid on the side of the airbox where power flap is(front bootom corner). There is a flexible rubber hose running to/from it...i assume this is the vacumn hose that causes the flap to open/close?

Anyone?

What actually fails to cause it to stop wrking does anyone actually know?

[silverRS4]

Three common causes. 1) the vacuum line that you successfully located can get pinched during vehicle assembly, rendering the solenoid unable to function. The solenoid receives its signal from the ECU, but with no motive force to move the diaphragm (from vacuum), the flap doesn't move. Since there is no sensor on the flap, the ECU has no idea the flap didn't move even though it sent a signal and the electrical circuit is functioning. Cause 2) The electrical circuit is ok and the solenoid has motive force (vacuum) but when commanded to open, the flap doesn't move freely in its housing. So it either sticks (usually sticks 'closed' since a return spring inside the diaphragm is fairly strong) or it doesn't move its full 90 degree rotation. Cause 3) The vacuum system has a leak. So when the solenoid is commanded to operate, there is not enough motive force to move the flap. The leak can be a split or damaged vacuum line anywhere in the system or it can occur when the the vacuum lines are disconnected from the solenoids on the exhaust mufflers (back boxes) and not properly plugged or capped.

Cause 1 and 2 affect the air box flap only. Cause 3 can be the most serious since the manifold tumble flaps will also be affected by the lack of vacuum. If per chance the leak is due to un-plugged exhaust solenoid lines, the leak will be sporadic since the signal to open/close the exhaust flaps is RPM and gear dependent. I've seen cases of this not resulting in a MIL and being tricky to diagnose.