resonance flap

ROB.S · 29th April 2001, 17:23

can anybody tell me the best way of checking if this device is working,should it operate on starting the engine,and what is the most likely cause of failure? thanks...oh yes mine is a 3.8L motor.

Hattar · 29th April 2001, 21:12

Hello,

Have you seen www.m5springboard.com / Useful info / ... Technical Bulletin? My flap makes only one, not two, test movements after start. Some other M5:s with well working flaps also do only one test movement.

My flap (3.6 l -89) did not work because the full throttle sensor was broken. After changing the sensor (~80,- Euro) my flap worked fine and I could notice a clear power step from 3/4 to full throttle at abt. 3500 rpm. If you suspect your sensor I can help you. I have documented the pins in a file including some comments. Just let me know (=your e-mail address).

Easiest check is to look at the actuator when you give full throttle from idle. I did not need to hit the rpm limiter before I could see the valve open.

You can also disconnect the vacuum hose to the actuator and take a ride. Do you feel the difference?

The actuator itself can be checked by sucking in the vacuum line. It should move quite easily.

Many people recommend to check the vacuum lines.

Good Luck,
Christer

Alan Archer · 30th April 2001, 10:15

HI...what makes you think that the flap isn't working correctly in the first place ?
Do you have a problem with mid range pick up or something ?
I was checking my 3.8 over this week for a track day and for the first time (in 2 years) when I reved the motor quite hard (ie. 4500+) I saw the valve move.
If you suspect it's not working you could simply mark the ends of the valve with paint or grease, take the car for a run & see if the valve has moved & hit the stops.

I know personally I can always tell when the valve operates by the change in engine note.
Any problem is likely to be mechanical, ie vacum hose split/blocked or solenoid valve faulty...(trace the pipework..)

Hope this is of some use.
Regards,
Alan Archer.

ROB.S · 5th May 2001, 09:56

thanks for the comments guys. after some investigation it turns out to be nothing more than a perished vacuum hose,but needed to take the chamber off to see it. flap working ok now and engine noticeably nicer to drive!