Hey guys,

First off, I want to say that I am obviously new to the forums, and new to owning my '97 A4. I bought the car a couple weeks ago and am thoroughly enjoying it thus far. I have followed directions found on this site and have done some of the DIY's (Cone filter, Boost gauge, etc.), but now after completing some searches I am lost, and I'm hoping to find a little guidance.

Problem: When i begin to accelerate an my the car starts boosting, I hear this horn sounding noise. I narrowed it down to the car boosting, because when it hits the '0' mark on the gauge it makes the sound. If I feather the petal, and hold it on the '0' it will continuously make the sound.

Any idea's would be great. I'm just not 100% sure where to start. I have full intentions of using the "boost leak test" DIY this weekend, and I'm hoping to find no leaks.

Also, I've seen it said a couple times, but when I go full throttle, is 4 lbs relatively accurate for a stock car?

Thanks in advance, and I look forward to growing with this community.

 

First off, the honk could be nothing more than resonance from the cone filter - my 300ZX had that as well when I went to a twin intake setup. Z guys referred to it as the goose honk.

Second, you're in safety boost. You should be at 8-9psi. A boost leak check is a good first step, as well as getting your ECU scanned for any codes.

 

Thanks for the reply.

Unfortunately, I don't think its the cone creating the noise. It did it prior to me installing it. I just couldn't get a handle on it. Now that I've installed the boost guage, I can pinpoint that it literally only does it right in the middle of the Vaccum/boost. 1 psi up or down, it wont do it.

I appreciate the suggestion for the boost issue. I will have it read later today. Is there a common occurance that will place it in the safety boost?

After more reading, I realized I was off on my comment regarding the boost deal. I am learning a lot right now, and have no mechanical experience prior to this car. I`m officially addicted to ripping it apart in my garage, and studying the haynes manual. Haha!

Thanks again.

 

Thinking it over, if you're getting that honk, have no check light or codes, and you're at only 4psi, a boost leak check is your best plan. It does sound like that is the problem.

 

We've created a monster. The 1.8T has a way of doing that to people. Before you know it, you'll be doing your own timing belt, control arms, and who knows what else.

To the issue at hand, I'm going to agree with Devil about the boost leak, but scan for codes anyway. Your local AutoZone or similar will do it for free, just make sure you write them down.

Did you have the mysterious horn before you installed the boost gauge? If not, then I would tend to believe that you left something open when you installed it. Make sure all your lines are tight. Also, make sure the hose clamps are tight from turbo to intake manifold, there are a few of them. I left one loose after I did my TB, and I had a similar noise and lose of power, but at a higher boost. Once I found the loose hose clamp, all was good again.

Hope this help, welcome to the forums. If you're truly addicted to you new toy, then stick around for awhile. So much to learn, so much to do, and so much help here it's ridiculous.

 

Thanks Brad, you have no idea...

I`m already on the fence about buying the turbo upgrade kit from Mike, and have already ordered a bunch of stuff for it. It has higher mileage, so I`m having a compression test done this week to make sure it can handle some upgrades. I am fairly stoked about this car because it isn`t my daily driver, and I can finally afford to mod a car. It was this or a DSM, glad I picked the Audi, I love everything about it, so far.

I am going to perform the leak test either today, or tomorrow. I have spent the better part of the morning mapping all the vac lines.

This noise wasn`t noticed on my test drive, but my first run after getting it home I noticed it, but I don`t think it was quite as severe. It seems to have amplified since doing the ``mods``.

If it were a boost leak, would it hold steady at 4lbs? Regardless of what RPM, or gear I'm in, it only ever boosts to 4lbs. I'm going to have the codes read now... this should be a new adventure.

2 weeks ago, I'd never done an oilchange, or changed plugs. I can't wait to do a bigger project on it. hahaha... I've got all the right tools now.

 

IIRC, a bad diverter valve (DV) can cause a honking noise and a cone filter will usually amplify DV sounds, pull that out and see if the diaphram is torn.

 

I think you're right. Could also be contributing to the 4lbs of boost as well.

 

^+1

Despite not being a 1.8t guy, from being on here for a few years now I've picked up a few things about the turbo motor and when I read the OP first thing that came to mind was DV. I almost would be curious to know if maybe the previous owner of the car has a BOV on there, which, if I'm not mistaken, would cause both the honk sound and, if it's venting 100% to atmosphere, cause the ECU to be all sorts of confused, sticking you in limp mode. Give the DV a look and if its not marked with any aftermarket brands like 'forge' or the like, chances are its probably stock and what McGov said will be a wise choice. Either way though, whether its a defective stock part, or a rice BOV, you'll want to get a forge 007 or equivalent DV in there, especially if you plan to go further with the mods

Hope what I've said isn't misleading, maybe some of the other posters in here can confirm or correct what I've said so we both can be clear on my statements lol

 

Diverter Valve is a good spot to check as well... should have mentioned that as well before.