Weird "Fog Horn/Animal Call" Noise coming from intake - Honda Prelude Forum

ion_four · 03-03-2009, 04:02 PM

Car:
99 Base w/JRSC, short-ram intake, P28/Hondata, no internal mods to my
knowledge.

Symptoms:
Recently, the engine has started to make a very loud and sustained sine
wave sound of probably around 300-350Hz ("Oooooo") It is loud enough that
I can hear it over road noise and the stereo when I'm driving down the road.
At first, I actually thought it was part of the new electronic album I was
listening to. lol I can hear it is coming from the intake pipe, when I produce
the sound while under the hood.

It occurs at sustained medium vacuum (10-15" on my gauge) when in or out
of gear, and ceases when the transmission is taken out of gear and the
throttle is blipped. It first did this when it was really cold out a couple
months back, and only did it once every few weeks, but now happens every
time I drive the car. The car idles well and doesn't have any driveability
issues at present.

Possible Diagnosis:
I'm thinking it's the JRSC bypass, but could it be the IACV, or possibly even
the EGR, since this is not doing anything as I'm running a P28 ECU?

Has this happened to anyone else? I didn't find anything in a search for
farts, burps or animal calls

Tee-Dot · 03-03-2009, 04:05 PM

You need to join the off topic forum if you want to read about farts and burps.

That said, sorry I can't help you. But you're smiling, right??

lilbill97 · 03-03-2009, 04:34 PM

Quote:

Originally Posted by Blacklude1

You need to join the off topic forum if you want to read about farts and burps.

That said, sorry I can't help you. But you're smiling, right??

animal call? maybe thats how you got that meat build up you had it your header blacklude1? did your Search intake suck up a raccoon?

Tee-Dot · 03-03-2009, 04:46 PM

Quote:

Originally Posted by lilbill97

animal call? maybe thats how you got that meat build up you had it your header blacklude1? did your Search intake suck up a raccoon?

Hmmm... perhaps.

ion_four · 03-03-2009, 05:00 PM

Wow, I guess this is just the comedy thread of the day

I actually just drove the car to school (there now) and it seems like the fog
horn starts at the transition into boost and then persists. I tried to record it
with my cellphone, but as you'd imagine, the sound quality is abysmal. More
static than anything else...like a video of sasquatch!

I'm really leaning toward it being the bypass valve, which sucks, since the
IACV or emissions equipment would probably be easier to fix

ion_four · 03-04-2009, 12:01 PM

Mooooo?

But, seriously...has anyone had a JRSC bypass go bad on them?

alblude · 03-06-2009, 07:27 PM

sorry, just saw this. the noise is coming from your fast idle valve. The JRSC inlet connects the IACV and fast idle via a groove which seems to cause that annoying resonating sound. after putting up with mine for about a year my Fast Idle valve went bad and I was getting the idle fluctuating problem. I went with Erick's TB which doesn't use the Fast Idle valve and rerouted the IACV intake.

ion_four · 03-07-2009, 04:31 PM

Interesting, thanks for the tip!

I'll have to look into bypassing this, as it may or may not even be doing what it's supposed to, since I'm not running the stock ECU.

I'll update this when there's something further to say!

blk97ludeSH · 03-15-2009, 03:21 AM

what if we just completely block the bottom of the TB? Thats what i did when my fast idle valve went bad. but i still have that noise?

ion_four · 03-15-2009, 12:50 PM

I take it you also have a JRSC? I haven't investigated any further, since I've been very busy, but I'm leaning toward the noise coming from the SC bypass valve.

I recently put a new serpentine belt on my car and when properly tensioned, I was seeing 8-9+psi with an upgraded pulley. However, it's suddenly gone back down to ~6psi. So, either the belt has stretched enough in ~2 weeks and <200 miles to reduce the peak boost by 2-3psi, or the bypass valve is somehow failing.

Possibly, NOT coincidentally, the animal call has occurred much less often and seems lower in volume, since the peak boost has gone down...hmm.

There's also the possibility that your/my problem lies in the IACV.

blk97ludeSH · 03-16-2009, 12:39 AM

I have not problem with the boost at all. I have constant 9-10 psi according to my gauge. You need to re tension the belt after you break it in, and are you using gatorback belts?

On other interesting fact that I had was... I took off the IAC valve and cleaned it with break fluid. before I let it completely dry I just slapped it back on and took it for a drive. every time I got off the gas the idle dipped drastically which i wasn't afraid of... but anytime there was any vac at all whether i was in gear and off the gas or when i was @ a stop. anytime there was vac the noise sounded. I let it sit for about 30 minutes after driving it for about 15... Idle went back to normal and the sound only came on a handful of times after that.. and not every time there was vac... to me I think its a bad IAC valve. I'm going to get a new one and test it out and also mess with the adjusting screw. I keep you posted.

ion_four · 03-16-2009, 01:08 AM

I am using a gatorback belt and I know it should be re-tensioned, eventually, but wow it's only been a couple weeks and I thought it was pretty taught to begin with!

In general, seem to have CRAZY belt slipping issues...I think my pulleys may be worn smoother than they should be, or some other crazy reason may be the cause. I replaced one of the pulleys (on the jackshaft) because it was inexplicably chewed up and was fraying the edge of the serpentine belt, this is when I put on the gatorback belt.

In any case, I put a new serpentine belt on the car when I got it, and only 4k miles later, it was slipping like hell, even when re-tensioned. I'd get close to 0psi at redline. I tried some "belt dressing" spray and this got the boost back up to 6+ psi, but the belt made so much noise it was almost comical.

That was truly odd, since belt dressing is supposed to STOP squeeling. Apparently (despite showing a ribbed serpentine belt on the car) this type of belt dressing is only for "old style" V-belts, or so I hear. Recommendation: don't bother with it, it just makes a mess.

Now that I switched to the famous gator-back belt, it was great for a few weeks, but back to 6psi at present.

This coming weekend I want to go to autocross, but (since I'm too lazy to wake up early on the weekend and) I need to investigate a few issues on the car, including this weird intake noise (though, I'm sure it wouldn't be an issue at autocross), I'm going to skip it. blah.

As a side-note, since you mentioned yours not occurring in boost, my engine seems to be making the noise in vac. or low boost, but it really just starts when the engine is transitioning, one way or another, and then persists.

I suppose I'll make a block-off plate for my Fast Idle (and EGR, while I'm at it) and investigate the IACV, as much as I can. If it's shot...ugh. Maybe I'll see if one from a Civic will work, since I have a few of those kickin around.

alblude · 03-16-2009, 01:20 AM

now that you mention the adjusting screw, I thought of a test you can run, but probably only work if you have an management system that you can control the IAC duty cycle through. If you do have that, than turn the adjusting screw all the way in so that port is completely closed. You're probably thinking "My car's gonna die you dumb ass", but shouldn't because the lower port is connected to the same one as the top and the IACV will get it's air from that, you might just have to raise up the IAC duty cycle a bit if the revs drop a bit too low.

Now that you have only one port open maybe the sound will go away if it was caused by the turbulence.

You can go and buy or clean the IACV/bypass valve if you want, but I never touched mine but I no longer have that annoying sound now that I sealed off the JRSC inlet