The civic rattle problem
 

I'd prolly be best in recording my audible impersonation of how this rattle goes... It's when you're accellerating, -- it seems to be worse at lower RPMs. I think it's in the exhaust. Anyone know what I'm talking about? It's happening on my friend's '96 Civic sedan (LX trim I think) and on my '93 Civic VX. I thought it was the loose heat shield but I removed that and it still makes that rattle. Any clues on how to get rid of it would be great!

yours,
the new guy who is an endless source of questions.

Does it sound like shaking a tin can with a couple of bearings in it? If so, it may be detonation/pinging/knocking.

I don't think its knocking. It sounds like a rusty piece of metal vibrating against another piece of metal? I thought maybe it was a common problem since my friend's '96 Civic and mine both have the same rattle. Maybe it's not quite a rattle, but a somewhat annoying noise. The heat shield that goes over the dip stick on my engine was loose. We all thought that it was the heat shield rattling against the engine. The sound the car is making definitely sounds like that would have been the culprit, but it wasn't.

There is no "knocking" sound in the rattle. More like a tin can filled with gravel or many teeny nuts. Sort of a chattering of teeth type frequency.

What side of the engine compartment is the noise loudest? You could have a bad bearing in the tranny. If the noise goes away when you disconnect the engine from the tranny with the clutch (meaning pedal to the floor), then it is probably one of the ball bearings on the mainshaft. My VX was making a horrible sound until I replaced the mainshaft bearing. Hope you don't have the same problem - it's not easy to get at.

My vote goes for detonation. try running the highest octane gas you can get and see if it goes away.

My friend thinks it's in the exhaust. Something rattling-piece of metal. The rattling isn't affected by the clutch. I think it has to do with the RPM the engine is at--maybe because at certain low RPMs there is more vibration. Anyway--might locate the problem today (I'm about to leave to Jiffy Lube where my friend works to do some engine cleaning!) tune up improved the idling and the overall performance of the car-- have yet to put in the V-Power spark plugs I bought online.

It isn't detonation. There are multiple heat shields on the exhaust system. Which one(s) did you remove? Get under there and check them all out. Some are fixed to the body and I'm not sure how hard they are to remove. If one of these has a crack in it (like mine did), it will cause the buzz when the natural frequency is reached.

The first one to usually buzz is the front side (nearest the radiator) of the Catalytic Converter. Then the one where the shifter is on the car and very rarely (although I have seen it before) the one nearest the gas tank.

The shields under the car are held to the unibody by really rusty 10mm bolts that like to snap really easily. The shield on the Cat can either be held on my rusty 10mm bolts or by a small stitch weld.

EDIT: There could be a rattle from the factory resonator or the header pipe leading to the B-pipe (the pipe in the middle of the car that houses the resonator) The factory piping from the down pipe from the head is double walled and can internally corrode and break a small junk off and rattle. Basically the same can happen with the factory resonator.

well my friend's Jiffy Lube friend said there is a pipe inside the tailpipe and that is probably what is causing the rattling. Anyway, I have bigger problems to deal with now. :( But thanks everyone for the input. Seems the car might need a new clutch. Dunno how much that will set me back. The idling problem I was talking about: The RPMs staying up after you depress the clutch before shifting and the slight lag in power (it's getting worse) when you accelerate at low RPMs. And the slight loss of power while cruising at highway speed (and then the slight surge in power)--all these things, I'm told, are signs of faulty clutch. What do you guys think?