KA Buzzing noise from engine bay

[project90]

I'm pretty sure it's not the timing chain guide, since it's more of a buzz than a rattle. Here's the wierd part, i only hear it when the engine is at certain RPMS. I've heard it pretty consistiently at 2900-3100, 2000-2100, and 1500-1600. Although it is harder to tell at speeds with the BRM, i think it occasionally happens at 4000. There were some threads saying it was the heat shield, but no cases of it happening consistiently at certain engine speeds.

Think it's the heat shield, or does anyone think it's a more serious problem like the valves?

oh, 1992 s13 ka24de around 50k miles

check the sig for more info

[onosqv]

Does this happen in neutral also, or only when the car is driving under load?

If you are able to reproduce this w/ the hood popped/car in neutral/park, then you can narrow down where the sound is coming from.

Valves I believe will increase w/ RPM increase.

[project90]

yeah, i could also hear it with the hood popped in neutral. The last time my friend and I tried listening to it (one revving, one listening closely over engine bay) I couldn't pinpoint it, but it sounded like it was coming from around the head. Didn't think about the exhaust manifold cover until now, so it could have been that too.

My car is in San Jose while i'm up at school in Portland. I'm going back for a week in October, and was just tryin to figure out what to do before I get back.

[Kenrik]

yeah, i could also hear it with the hood popped in neutral. The last time my friend and I tried listening to it (one revving, one listening closely over engine bay) I couldn't pinpoint it, but it sounded like it was coming from around the head. Didn't think about the exhaust manifold cover until now, so it could have been that too.

My car is in San Jose while i'm up at school in Portland. I'm going back for a week in October, and was just tryin to figure out what to do before I get back.

You don't need two people... just tug the throttle in the engine bay...

I bet it's the heatshield...

[onosqv]

Use a long screwdriver or the doctor stethoscope (sp?) thingy to try to narrow it down. You'll find out if it's an internal engine thing or heatshield real fast.

Simply taking off the heatshield and checking is an easy way too .

[DjPantsSpecR]

my biggest heatshield problems were from not the upper heatshield, but rather the lower part that is bolted onto where the two sections of the exhaust manifold meet, pretty much the downpipe of the exhaust manifold...

i had another piece down there that buzzed too, and its always at consistent engine speeds, you can tell when you are about to buzz then its a probably a heat shield.

Or just get a tube and put it up to your ear, that works well to find all kinds of noises, and its pretty much free

[Sygerwulf]

I dunno if this is the same on all models or not, I'm assuming it is because my exhaust is stock until after the heat shields, but mine started to buzz and rattle and I discovered that there was some heat wrap in between the exhaust and the heat shield. Over time the wrap had deteriorated allowing lossness inbetween the two. I know this doesn't help but that's what was happening to make mine vibrate.

[project90]

thanks for all the help guys, the heat shield will be the first thing I look at when I get back home!<3 from portland

[DjPantsSpecR]

sygerwulf, great point. that stuff is on neither of my s13 motors, but it is on both my s14s

[KADET4134]

I bought my 93 240SX SE coupe about 4-5 months ago and the only problem I encountered was a loud, abnoxious buzz that went off around those RPM's you were talking about. I asked the girl who was selling the car and she said she took it in and the mechanics said it was the heat shield. So I took off the heat shield and fiddled with it and put it back on tight. The sounds did not stop. A month or so later I had my exhaust done, a 2.5 inch. catback (before I decided to go turbo) and when I drove it away from the shop, the sound was gone. I personally believe the muffler is crap after a fair amount of miles and there are pieces that come apart inside the muffler that rattle. It does not sound like the muffler at all it sounds as if it is coming from the engine bay or close to it. That is the only thing that would make sense, as I hadn't altered any other aspect of the car but the piping fron the cat back and the N1 muffler.

[DjPantsSpecR]

i just gotta reiterate

not the heat shield that you can easily remove, its near where the lower half (similar to a downpipe) bolts to the lower exhaust manifold

and there are more heat shields down the way. I'm gonna go out on a limb and say it wasn't the muffler...