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Old 07-24-2009, 10:26 AM   #1
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Strange noise - can anyone explain?

New to the forums... be gentle!

I've just upgraded my 99 for an 05 model, which is obviously a very different design inside and out. I've not driven one this recent before, but I've noticed a strange noise coming from behind my right ear (I'm in the UK so right-hand drive) when I put any pressure on the accelerator. The best way I can describe it is it sounds like a piece of paper flapping in the wind. It's not a rattle, just a sort of quiet flapping noise that only happens when the accelerator is pressed, even at low speed. Can't really tell whether it's there at high speed because the sound of the engine is too loud. I'm driving with the hood up.

It's not something I ever heard on the 99 car, but then again the interior and engine were both different.

The new car is a 2.5 Tiptronic.

Thanks for any suggestions!

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Old 07-24-2009, 11:37 AM   #2
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does it only happen when you accelerate, if so up to what speed and what geer/geers? Does it go away when you let off the accelerator? Does it only happen when your moving? Does it happen when you have the top up and down? Does it happen when you slowly accelerate?

I am just trying to gather more info to eliminate things like seatbelt being caught in the wind, something loose, like trim piece on the car....

I would first take the small screw out of the top of the air vent behind you/front of the rear wheel, take a flashlight and look in there for anything loose or flapping. Might want to check the other side too. it is real easy to take them off. I doubt thats it but you never know. This maybe one of those process of elimination things.
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Last edited by mptoledo; 07-24-2009 at 11:56 AM.
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Old 07-24-2009, 12:19 PM   #3
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Hi, thanks for your reply.

I've just been out for a drive to try to gather some facts, and this is what I can add.

1. I can hear it in all gears, and at all speeds - from a crawl to at least 60mph, which is the fastest I can go on the roads around here.

2. It's definitely related to acceleration, either fast or slow acceleration. It's just about possible to drive at a careful, steady pace without hearing anything, but if I then give it a fraction more gas then I hear it again. If I let off the gas, it immediately stops.

3. If I stop and put the car in neutral then it's much, much less - only if I rev it quite a lot do I hear anything, and it's far less than when the car's in gear.

4. I don't hear anything when the hood's down, but then again it is pretty quiet so that may be a red herring. However, I **can** hear that the right-hand air intake is much louder than the left-hand one. In fact, it sounds like a vacuum cleaner, whereas the other one is very quiet. I don't know if that's significant.

It's darkish at the moment so I'll leave the exploration with a screwdriver until tomorrow or the next day!
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Old 07-24-2009, 12:59 PM   #4
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one side is intake and the other side is exhuast. so one side will be louder. we can rule out anything loose on the car and "flapping" in the wind. We now have to get down to the mechanics and hopefully one of the mechanics on here will chime in, as this isn't my strong point.

Does it sound like air escaping? I am only guessing here as I stated I am no means a mechanic(just a good problem solver), but it could be anything from air pressures, cracked head(doubt it), transmission(boubt that too) to something with your acceleration throttle.

I am going to stop guessing as this is now out of my league. So please one of you knowledgeable mechanics, Please chime in.
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Old 07-24-2009, 01:08 PM   #5
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Thanks for your help, mptoledo - much appreciated.

If anyone is able to offer any further assistance, that would be great. I do have a warranty on this vehicle from the dealer that I got it from so hopefully any problems can easily be sorted.

It's really hard to describe the noise I heard. It isn't a rattle, and it isn't a knocking. It's very faint, more like a fluting/fluttering noise, or you could maybe describe it as a really quick tapping noise. It's not metallic in any way.
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Old 07-24-2009, 06:17 PM   #6
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Good to hear your under warranty. I would first try driving a similar car to see if it is something common in that model year. Just find a similar model at a dealership and see if its the same noise. Also, do you know the previous owner? I would make sure they didn't put any mods on, ie.. exhaust upgrade, flywheel, or anything else. Then don't hesitate to take it to the dealer.

Last thought and its a long shot. could it be tire noise? I have heard some strange noises coming from tires. try driving on different pavements. Usually if its tire noise it changes frequency the faster you drive. Kind of like when you put baseball cards in the spokes of your bicycle when you were a kid(might be an American thing ).
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Old 07-24-2009, 07:45 PM   #7
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My GF's 2006 Tiptronic Boxster is experiencing the same thing I believe that you are describing. It's not a rattle and not a knock. She mentioned it the other day and I sat in it and heard something. I was going to take it in sometime to have it checked out as well. If you find out what it is, could you please post back. I will do the same if I find out before you.
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Old 07-25-2009, 11:29 AM   #8
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I found this on another site, see if it sounds familiar. They describe it as a howl. see link below for full thread.


You may have to join to view, but it is free and painless. Decent site.
http://www.babblers.org/forums/showthread.php?t=9838

In my case it turned out to be a bad right rear wheel bearing. If you stop by the dealer or other mechanic they should be able to diagnose it for no charge. I had hoped it was just tire noise as it didn't seem to change much based on side loading. A test drive at the local dealer and subsequent inspection of the tires showed it most likely to be the wheel bearing and $500 later the noise was gone.

Here is another "hissing" sound thread:
http://www.babblers.org/forums/showthread.php?t=9998
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SO, GROW A PAIR NANCY AND DRIVE IT LIKE YOU STOLE IT!!
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Last edited by mptoledo; 07-25-2009 at 12:33 PM.
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Old 07-25-2009, 03:01 PM   #9
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Thanks! I think the hissing one is probably more on the mark than the howling one, but it still sounds like it's a physical (mechanical) thing rather than escaping air. I've decided I'm going to swing by my local Porsche dealer next week and ask them to take a look, which is probably no bad thing anyway given that I didn't get the car from a Porsche place. If there is a problem, I'll go back to the place I bought it.
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Old 07-25-2009, 04:37 PM   #10
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I thought I had read somewhere regarding the vent line to the gas filler inlet coming off or cracking.
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Old 07-27-2009, 05:58 AM   #11
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Well, I had the car examined by Porsche this morning and it turns out the noise was nothing to worry about - an operational engine noise that can sometimes be made by the fuel injector systems, apparently. Which is good news. I'm really pleased I had it checked out, even if it did lighten my bank balance a bit, because now I can enjoy the car fully without worrying. The only items the report turned up was non-standard tyre foam and that the previous owner had inexplicably disconnected the front boot/trunk light, which they've rewired for me.

Thanks for all your help, guys - this forum has been a discover and I intend to stick around, either for future problems or to see if I can help or advise anyone else.

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