arren123

My ITR just started to make a new noise about 1 month ago.
This rattling noise ONLY happens after the car has warmed up. (About the 2nd line after the C on the temperature gauge). It happens right around 4000 rpms in or out of gear, whether the car is moving or standing still. I can hear it faintly past 4000 rpms, but its its loudest at 4000 rpms. If I leave it at 4000 rpms, the sound is constant. It doesn't change its frequency or volume.

I'm trying to pinpoint where its coming from, but I'having a little trouble.
I thought it might be the heatshield underneath the car above the cat.. The heatshield seemed a little loose and it was cutting up the O2 sensor wire insulation so I removed the heatshield. After that, the car still makes the same exact noise.

Next I warmed up the car and stood in front of the engine bay. I pulled on the throttle cable until it was making the noise. It sounded it it was coming somewhere around the intake manifold area but I couldn't locate the exact location. The normal engine noise was too loud.
It sounded bad too -- I guess it kind of sounds like the rattle you hear from a GS-R's exhaust manifold where the inner pipe is rattling except it sound like its from the intake side.

I have a stock intake manifold and a AEM CAI without the relief valve. So I'm pretty sure nothing got sucked up the intake. The car runs fine and it doesn't seem to have any loss in power or accelleration. It still pulls hard.

Is there anything I can do that will help me narrow down where the noise is coming from?

Bbasso

Ok I'm lost...

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by arren123 &raquo;</TD></TR><TR><TD CLASS="quote">
I have a stock intake manifold and a AEM CAI without the relief valve.</TD></TR></TABLE>

How can you have both on the car at the same time???

Now that rattle, Turn the car off and let it cool. then go under the car and start banging on things and see if you can pin point it. I've done this method plenty of times and usually works.

MattD@Stoptech

Cause intake manifold is an intake manifold...and j00 suck at reading?

arren123

Quote, originally posted by arren123 »

I have a stock intake manifold and a AEM CAI without the relief valve.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Bbasso &raquo;</TD></TR><TR><TD CLASS="quote">

Ok I'm lost...

How can you have both on the car at the same time???
</TD></TR></TABLE>

Don't take this as sarcastic, but the intake manifold and the AEM CAI are two different things.. The AEM CAI attaches to the throttle body that's attached to the intake manifold.

Oh.. Yeah.. good point about banging around. . I tried taking a rubber mallet and banged on the cat and heat shield, the exhaust piping, the front sway bar, and the transmission but couldn't find anything that would rattle. Maybe I'll try hitting the intake manifold too, but i don't think I'll find anything there &lt;shrug&gt; . I though that it might be coming from the piping of the AEM CAI hitting the A/C piping, but the a/c pipes aren't touching it. I have them zip tied together so it doesn't touch the AEM pipe.

Any other ideas? would there be anything inside the intake manifold that would start to rattle after the engine warms up?

ITR184

If it doesn't happen until it warms up I suspect the emissions system. I would check the EGR valve.

Bbasso

me= for reading without comprehending

mstewar

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by arren123 &raquo;</TD></TR><TR><TD CLASS="quote">Any other ideas? would there be anything inside the intake manifold that would start to rattle after the engine warms up?
</TD></TR></TABLE>

nothing inside the IM should be rattling.. at least not in a difference between being warm and cold..

got a good set of jackstands? put the car up, start it up and climb underneath.. have a friend push the throttle and see what their is to see from there..

i know it's on the wrong side, based on where it seems like the noise is coming from, but maybe make sure the lower portion of the CAI isn't rubbing/hitting something as well..

arren123

Thanks to all! Those are all very good suggestions.. The one about checking the Emissions system sounds plausible since it only happens when the engine is warm. I'll check that system as well.. I just hope its just as simple as tightening a bolt or something dumb like a bolt came loose and fell out.

MattD@Stoptech

HAHA!

EGR valve on a b-series....um...I dun think so...

ITR184

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by El Pollo Diablo &raquo;</TD></TR><TR><TD CLASS="quote">HAHA!

EGR valve on a b-series....um...I dun think so...</TD></TR></TABLE> Thank for the lesson

What about the knock sensor? Do you have a check engine light illuminated? Should give a code 23 if thats the problem.

arren123

Nope.. No CEL. hmmm.. i wonder.. maybe it is really knocking or pinging I'm hearing? Would knocking/pinging sound similar to a rattling?
But I would think if its knocking/pinging, it would continue to sound bad from 4000 rpm all the way up to redline. I guess I'll pull the spark plugs out to make sure nothing funny is going on in there.. This noise occurs with no load on the engine.. So I think knocking/pinging would be far fetched..

ITR184

IF your not getting a cel I doubt that is your problem. My thinking behind the knock sensor was maybe the timming wasn't retarding after warm up, and at higher rpm's. This noise occurs with no load on the engine.. Yeah, so there goes that theory. I was thinking loss motion device, but after Vtec engages you wouldn't here it any more. I don't know what the odds are in one going bad is(probably pretty high)? Good luck with it. Sorry I wasn't much help.

SLCTyper

I've got the exact same problem but I didn't notice it until after I had my transmission taken apart and had a JDM final drive, Quaife, new flywheel, and clutch installed. After about two weeks I would notice that when the car got warm it would rattle like hell from about 3500-4000 rpm and then dissipate as I accelerated or shifted gears. It doesn't seem to do it all the time though and just like aren123, I can't seem to pinpoint the source. Not trying to hijack the thread or anything, but thought my experience might help someone diagnose the problem.

arren123

Do you do the transmission work yourself? Maybe there something in that general area that was taken apart and was put back on and was loose or went out of alignment and now its rattling against something.. I'm pulling at strings now..
Maybe if we knew what was touched, it could help pinpoint the problem.

I remember having my clutch replaced at 49795 miles.. But that was at least 2 years ago with no rattling noise.

SLCTyper

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by arren123 &raquo;</TD></TR><TR><TD CLASS="quote">Do you do the transmission work yourself? Maybe there something in that general area that was taken apart and was put back on and was loose or went out of alignment and now its rattling against something.. I'm pulling at strings now..
Maybe if we knew what was touched, it could help pinpoint the problem.

I remember having my clutch replaced at 49795 miles.. But that was at least 2 years ago with no rattling noise. </TD></TR></TABLE>

No, unfortunately I wasn't brave enough to do that much transmission work myself and had a local speed shop do it. I thought the same thing that there might be something loose, but considering the sound isn't consistent (sometimes I hear it, sometimes I don't) I don't think that is the case. Its got me stumped though. When I do hear it, the noise level is proportional to the acceleration. It is quieter at 1500 rpm then gets progressively louder and seems to top out at around 5000-5500 rpm then the sound seems to tapper some from that point to redline. It doesn't seem to affect the way the car drives or handles, but it is really annoying to listen to.

arren123

I think I figured it out. I was driving to work today and contemplated the problem again. I know I have a faulty thermostat because the car takes a long time to warm up and the water temperature actually goes down when downshifting. This is especialy noticible with the cold weather in the east coast.
So.. It all makes sense if its the thermostat. . After the water temperature heats up, something in the thermostat might be rattling around the 4000 rpm range. The noise is coming from around the intake manifold area and the thermostat is in that area.

If its really the thermostat then I think I need to get the thermostat replaced before it comes apart. Will a Pep-Boyz/AutoZone thermostat be ok? Or should I go OEM?

LootR0435

OEM or Mugen. OE is a little more, but worth buying over Autozone IMO(no-brainer in my book). Mugen is $$$ but does offer some advantages, especially when combined with rad cap. Good luck hope you found the prob.

arren123

UPDATE:
I finally replaced the thermostat today. That one bolt next to the main wire harness is a PITA !!! Ahem.. Anyway.. I let it warm up in my driveway. Then I took for a test drive. After about 3 minutes, I could still hear the rattle. Sometimes its as loud as before, but most of the time it is not as bad. So whatever I touched, seems to have dulled the noise a little bit.

The things I touched/moved around were - strut bar, intake, main wire harness, the starter bolt, the water house to the thermostat cap, the smaller house on the thermostat cap, the bypass hose from the intake to the valve cover.

I am very stumped.. I fixed the failing thermostat by replacing it, but I still have the rattle coming from somewhere..
Any possibility it may be coming from a broken rear engine mount? (I'm just pulling things from my butt right now. I haven't checked the rear engine mount yet)

bluk20

I have the same problem with my first gen b16 and can't fuigure it out, and its driving me crazy have you you found out what the rattle was.
My rattle only happens at very light throttle around the intake manifold
I cant here it when in vtec or heavy throttle. I have alredy pulled the Rod bearings and plastigauged them and they were in spec and had no weird wear marks on them just normal and the sound has not changed in 5 months
and sometimes the rattle is not that loud.

Rtzx9r

It is more than likely a heat shield or you need a valve adjustment. Both of these items are "harmonic frequency" sensitive with engine speed.

It is not going to be anything to do with coolant or thermostat- the noise would be muffled by the water.

I have fixed 3 heat shields on my DC4 and also done the valves 3 times. I bet it is one of the two.

JjuuN R

ok, i'm 97.998% sure you have a problem with a rattleing heat shield, thus why i took every single one of mine off... it'll only take you about 5 minutes to take all of them off, start it up let it get to temp. and see if it's gone or not.

if the noise is still there it'll take you 5-10 minutes to put them back on, or 0 mintutes just to leave them off which doesn't harm anything