Mystery Sound

I bought my 91 CRX HF in late august ...
it runs fine ... no problems with the engine or tranny

except this odd mystery sound ... its like a heavy rattling in my engine bay
i thought it could be the heat shield rusting away and rattling so i removed it
and it still makes this ugly sound

its most prominent in 1st gear around 3000 rpm and gets more and more
subtle as I shift up ... but its still noticeable ...

I just dont know what it is and its driving me insane ... help please :frown:

Does it continue even when it's warm, or does it eventually go away after a few miles? I know in my car, when it's cold, the wrist pins are loose and rattle until it gets warm enough for everything to expand.

nah man ... cold or warm ... doesnt matter ... sounds like it could be in the tranny ... but it doesnt kick in until the high 2's or 3000 ...

Does it continue even when it's warm, or does it eventually go away after a few miles? I know in my car, when it's cold, the wrist pins are loose and rattle until it gets warm enough for everything to expand.

Yikes! that's not normal, unless you are talking about low-silicon forged pistons.
As for the rattle, it's most likely the heat shield on your catalytic converter, or further down the exhaust...those are the more common ones.

Do you still have the factory exhaust manifold and "A" pipe? If so it might be the inner wall of the "A" pipe has broken loose and rattling around inside (does it sound like a ball bearing rattling inside a can?). I know this because mine does the same thing. It could also the catalytic matrix inside your convertor has broken loose. GL

Check your cat converter heat sheild. Jack your car up and wiggle it to see of its loose. Heres how to fix it:

http://fourthgenhatch.net/cat.html

I think i'll record the sound and post a link ... cause i've already removed the heatshields ... all that other stuff I have no idea ... I'm very car dumb right now

it doesnt really sound anything like a spraypaint can or anything ... its hard to explain ...

Yikes! that's not normal, unless you are talking about low-silicon forged pistons.
As for the rattle, it's most likely the heat shield on your catalytic converter, or further down the exhaust...those are the more common ones.
My friend (certified mechanic) seems to think it's fine. He says Mitsu Mirages do it right from the factory and that I have nothing to worry about. I'm not really worried about it, as long as I get another 6 months or so out of the engine I'll be fine.

My friend (certified mechanic) seems to think it's fine. He says Mitsu Mirages do it right from the factory and that I have nothing to worry about. I'm not really worried about it, as long as I get another 6 months or so out of the engine I'll be fine.

Do me a favor and go outside; look at the rear of your car. Is there a mitsubishi symbol on it? If so, you MAY be ok. This "mechanic" you are talking to, is nothing short of dumb. People seem to like to throw around the term "certified" like it actually means something. My friend Mike who is "certified" comes to me for his engine builds. Hey, he knows how to change a starter and rotate some tires though.

Seriously though, it's not normal. 6 months is wishful thinking, if it is infact a damaged piston/wristpin.

that sounds like the same problem i have. mine only happens when i accelerate quickly though.

yeah i was thinkin the heatshield round the catalytic converter myself..

i just cut the shield off of the cat when i put in my 2.5 straightpipe. i havent put my test pipe back on mine since i got it worked on but even with the stock cat it sounds beastly. im just glad i dont have e-checks

i just cut the shield off of the cat when i put in my 2.5 straightpipe. i havent put my test pipe back on mine since i got it worked on but even with the stock cat it sounds beastly. im just glad i dont have e-checks e-checks as in CEL? why would ya unless ur running without a o2 sensor?

Do me a favor and go outside; look at the rear of your car. Is there a mitsubishi symbol on it? If so, you MAY be ok. This "mechanic" you are talking to, is nothing short of dumb. People seem to like to throw around the term "certified" like it actually means something. My friend Mike who is "certified" comes to me for his engine builds. Hey, he knows how to change a starter and rotate some tires though.

Seriously though, it's not normal. 6 months is wishful thinking, if it is infact a damaged piston/wristpin.
Well it sounds like my friend has a lot more experience than your friend does. He actually builds his own engines (as well as changing starters and rotating tires). And I'm well aware that my car isn't a mitsu, and I was going to mention something about that but I figured no one would go with the same old bs of feeling the need to point it out; because it seemed pretty obvious. I just mentioned it to prove a point that it might not be that bad since other cars do it straight from the factory and run fine for a long time. But whether it's a mitsu, ford, or honda; engine components are relatively the same. They have pistons and connecting rods, and wrist pins. And the fact that the sound goes completely away after the car is fully warmed up to operating condition. But what do I know, I'm no engine building guru...

well my friend works at the local grocery store in the produce section and he can change spark plugs!! looks like my friend has more experience then both of ur friends *tongue out* haha!

But what do I know, I'm no engine building guru...

And, I am. Which is why I'm telling you it's not normal for your Honda motor. Besides, many mitsubishi pistons are forged, not hypereutectic cast pistons like honda pistons are, which is why they make noise.

e-checks as in CEL? why would ya unless ur running without a o2 sensor?


By e-checks he means emissions checks, aka smog tests. I wouldn't recommend running without a cat if your car is a DD anyway.

I think i'll record the sound and post a link ... cause i've already removed the heatshields ... all that other stuff I have no idea ... I'm very car dumb right now

it doesnt really sound anything like a spraypaint can or anything ... its hard to explain ...

*** With all the heatshields out I still think it's the "A" pipe or the cat matrix. (Edit 12-6) *** Try getting under the car with a hammer and lightly rap on the pipes. If you're lucky the suspect part will resonate. There is also a heatsheild on the backside of the exhaust manifold, did you removed that one too?

no sir i have not removed that one ... but i'll give everything a go-over tomorrow ...

Yay for not having heat shields...or a Cat for that matter :P

that sounds like the same problem i have. mine only happens when i accelerate quickly though.

yes ... thats when it happens the most ... and it wont really kick in when im turning until i straighten out ... any more ideas? :confused:

mmm, my heat shield over my exhaust manifold is off. the sound mine makes seems like its comming from my feet, or just on the other side of the firewall. ive been trying to figure out what it is since i got the car. at first i thought it was my pedals. i dont know if this sounds like your car, but mine almost sounds like a loose bolt rattling... it has gotten a bit worse since i first heard it.... can you describe the sound you hear any better?

mmm, my heat shield over my exhaust manifold is off. the sound mine makes seems like its comming from my feet, or just on the other side of the firewall. ive been trying to figure out what it is since i got the car. at first i thought it was my pedals. i dont know if this sounds like your car, but mine almost sounds like a loose bolt rattling... it has gotten a bit worse since i first heard it.... can you describe the sound you hear any better?

This could also be a loose rocker. Try doing a valve adjustment. A loose rocker sounds EXACTLY like a loose bolt.

hmmm ill check that tomorrow. any other ideas? could it acctually be a loose bolt somewhere?

hmmm ill check that tomorrow. any other ideas? could it acctually be a loose bolt somewhere?

Not sure...but does it get louder at WOT and you can barely hear it when you're just barely giving it gas?

yeah, exactly. its the loudest at low rpms

Well just as an epilogue to my mystery noise saga; I replaced the "A" pipe on my car and the noise is gone. GL

yeah, exactly. its the loudest at low rpms

I'm almost 100% positive you have a loose rocker by the way you're describing it. Do a valve adjustment. If you have the tools, it's very easy.

awsome, ill look into that.
now lets revert this thread back to fancypants, aka stnapycnaf =/

Could it spark knock? Try putting in 93 octane gas and see if it goes away.

well i've decided to have my friend check it out

he's a tech at a honda dealer ... so we'll see

yeah i have a friend that washes cars at honda..but he thinks he's a tech.. neways lol i do happening to know a few kickass techs at honda here in Reading ,Pa ..but yeah let us know what he says..seems that knocks n taps are the cool thing here on the 4th G forum for real tho good luck with it..Lord knows u dont need any bullshit b4 the holidays wit the transportation

nah bro ... he went to tech school in chicago ... and i've witnessed him work ... anyways ... jeah i'll get back at you guys with whatever he does/says and the results ... thanks