Need help diagnosing sound

Storm897 · Aug 28, 2004

I have a 2001 Manual Honda Civic Ex. It has 64k miles on it. It works like a charm. Never had a problem with it. All of a sudden about 5k miles ago I start hearing this sound. It only happens when the car is in gear and in the RPM range 3,500 through 3,800. It sounds like a rattling noise. When I rev my engine through that range and I am not in gear I dont hear the rattling noise. It only happens when I am in gear. It happens in all gears also. It is more noticible when I slow down (by braking, not using the engine and gears) and the car is still in gear. I finished doing a AutoRx cleaning cycle and am currently in the rinse phase. I am not sure what it is. What could it be? If you need more information I will be happy to provide it for you guys.

Thanks again in advance,
Oren

Dan4510 · Aug 28, 2004

Could be preignition.

EGR may not be operatiing just right.

May need to do a clean with techron, neutra, or fp.

Dan

Storm897 · Aug 28, 2004

quote:

Originally posted by Dan4510:
Could be preignition.

EGR may not be operatiing just right.

May need to do a clean with techron, neutra, or fp.

Dan

Thanks for the quick response dan.

I will pick-up a techron fuel system cleaner tommorow from advance auto parts.

Why would preignition only be happening in the 3,500 - 3,800 RPM region though?

Also, excuse my lack of knowledge but what do you mean by EGR?

I will check the gap on my spark plugs and re-torque my spark plugs to spec tommorow.

Oren

Storm897 · Aug 28, 2004

Just reviewed my excel spread sheet with all my maintence for my car and at 60,200 miles I used a Penzoil Fuel treatment, and at 61,200 miles I used a Lucas Fuel treatment.

I'm not sure that Techron will do any better then those 2 did. Correct me if I'm wrong please.

acranox · Aug 28, 2004

rattling noises from Hondas are very, very often the heat shield. There is a piece of sheet metal that goes over the exhaust to help keep heat from entering the cabin. What you've described sounds like it could be the heatshield.
It rusts and comes loose, and the usual solution it just to live with it, or remove it, since the heat shield costs a bit to replace, and serves minimal function.

rjundi · Aug 28, 2004

Your heatshield on your exhaust system is rattling, your time/mileage seems right for a failure. Real inexpensive to fix if you just tear it off. Very very common Honda issue.

Storm897 · Aug 28, 2004

Thanks everyone. Why would it happen only in a specific RPM range?
Also is it the exhaust heatshield or the header heatshield (under the hood). We also have a heatshield for that.

Thanks again,
Oren

Gary Allan · Aug 28, 2004

quote:

Why would it happen only in a specific RPM range?

Certain mechanical "harmonics" may be present at that rpm (something certainly is) and you are hearing the evidence of it. You've got all kinds of mechanical frequencies colliding all the time ...on occasion ..at specific rpms ...you get a resonance that manifests itself.

This is just the most resonable explanation.

Storm897 · Aug 28, 2004

Why would it happen only when I'm in gear?

When I rev my engine in that range and I am not in gear I dont hear any sound.

Thanks,
Oren

tpi · Aug 28, 2004

Tracking down noises can be tricky. If it does it only in gear does it sound like some noise which could be coming out of the transmission or clutch? I had a Mazda with a manual trans and got a rattle from transission in a narrow RPM band, but this was under load.

Then again resonant noises such as rattling exhaust system could be affected by whether engine is loaded by transmission or not. I bump various heat shields and exhaust pipes with my foot or hand, listening for the rattle. Catalytic converters can rattle.

Do you get the sound when the clutch is in,but trans in gear coasting?

Storm897 · Aug 28, 2004

Just checked the gap on my spark plugs and they were all right. Perfectly gaped. I also removed the header heatshield (the part on the left in the pic below) and drove around and the noise continued.

Picture

Storm897 · Aug 28, 2004

quote:

Originally posted by tpi:

Do you get the sound when the clutch is in,but trans in gear coasting?

Thats pretty much when I hear it. When I am in gear (clutch engaged), and my car is coasting (decelerating by itself).

Gary Allan · Aug 28, 2004

You should still be able to differentiate if it's a heat shield or not. It will be more of a "buzz" or a clang type thing. If you do find that it's a heat shield ...and are leery of removing it. Just get a long SS hose clamp (you can join a few if your supplier doesn't have the LONG ones) and just tighten it up. That's what the dealer did for my 86 Tempo under warranty. It worked well.

This may be one of those 'how many teeth are in a horse's mouth" (go and count them) type diagnosis. That is, you may end up locking down everything that could make this noise until you stumble across it.

Storm897 · Aug 28, 2004

quote:

Originally posted by Gary Allan:
You should still be able to differentiate if it's a heat shield or not. It will be more of a "buzz" or a clang type thing.

I removed the heatshield and the noise was still there when I drove around to test it.

Thanks,
Oren

Storm897 · Aug 29, 2004

quote:

Originally posted by Gary Allan:
This may be one of those 'how many teeth are in a horse's mouth" (go and count them) type diagnosis. That is, you may end up locking down everything that could make this noise until you stumble across it.

I am doing an auto-rx cycle, did 2 fuel system cleaners, gaped and checked spark plugs, and removed the header heatshield. I am trying to knock out all the possibilities one at a time.

Remember, when I am in gear (clutch engaged), and my car is coasting (decelerating by itself) between 3,500RPM - 3,800 RPM is where I hear the sound.

What other things could be causing this noise?

Thanks,
Oren

mechtech · Aug 29, 2004

Since you can hear the noise when braking, I can't see how it's pre ignition related.
Could be a throw out bearing or fork that is getting loose/dry and resonates under those conditions.
Noises can be tough to pinpoint. 5 minutes or 5 hours.

Russ · Aug 29, 2004

Any idea what area this noise is coming from? Sounds like heat shield could be a possibility. However, exhaust manifold is not the only exhaust system component that has a heat shield over it. Check the catalytic converter and any other heat shields that you can find along the exhaust system. Sometimes the fault can be obvious (like a broken shield that you can see). It may also be a good idea to bang on the areas around the heat shields to see if you can duplicate the sound.

tpi · Aug 29, 2004

but the instant you disengage the clutch the noise goes away? It follows engine speed, not whats going on in transmission or driveline? But it won't do it stopped in neutrl?

Got this right? Frankly noise diagnosis is difficult enough in person sometimes, let alone online

Nevertheless look hard at the clutch and how clutch action changes the noise.

Storm897 · Aug 29, 2004

quote:

Originally posted by Russ:
Sounds like heat shield could be a possibility. However, exhaust manifold is not the only exhaust system component that has a heat shield over it. Check the catalytic converter and any other heat shields that you can find along the exhaust system. Sometimes the fault can be obvious (like a broken shield that you can see). It may also be a good idea to bang on the areas around the heat shields to see if you can duplicate the sound.

Thanks to everyone who responded so far.

I removed the heatshield from the header and drove it around. The sound continued to occur.

I will check if the catalytic converter has a heatshield. It it does I will try and remove it and see if the sound goes away.

Thanks,
Oren

[ August 29, 2004, 09:36 PM: Message edited by: Storm897 ]

Storm897 · Aug 29, 2004

quote:

Originally posted by tpi:
but the instant you disengage the clutch the noise goes away? It

You exactly right tpi. The moment I disengage the clutch the sound goes away. I had the RPMs to about 6,000 and disengaged the clutch and didnt hear any sound when the revometer passed through the 3,500 - 3,800 RPM range.

quote:

Originally posted by tpi:
It follows engine speed, not whats going on in transmission or driveline? But it won't do it stopped in neutrl?

It wont occur when stopped or in neutral.
It only occurs when in any gear (transmission is working).

quote:

Originally posted by tpi:
Got this right? Frankly noise diagnosis is difficult enough in person sometimes, let alone online

Nevertheless look hard at the clutch and how clutch action changes the noise.

The sound is hard to pinpoint because I cant be stopped and have to be moving. Also, once I am around 3,500 RPM, in addition to engine noise I have to stick my head out the window slightly to hear exactly where the noise is comming from. This is hard because the wind blows in my face.

OFFTOPIC:
[When I had my head out the window I reminded myself of Jim Carey in "Ace Ventura: Pet Detective". ]

So I only know its from the front half of the car. I cant pinpoint further then that.

Thanks,
Oren

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