I have a 1992 Accord with manual transmission. The car has around 165,000 miles on the odometer and still runs well. But there's this sporadic clinking sound, like metal rattling or sheet metal rubbing against something, when driving. The sound seems to be coming from the bottom towards the front of the car, and happens only when the engine's warm. The sound is loudest when the car's going downhill. The strange thing is that if I depressed the clutch, the sound immediately stops. Sound returns as soon as I release the clutch. Also, there's no sound if I'm coasting downhill in neutral. The sound returns as soon as I put the car back in gear.

Does anyone have an idea on what may be causing this? I'm also wondering whether this type of noise can come from the resonator or catalytic converter when they're hot and and car is under a load.

 

 

Have a look at the sway bar bushings and upper a-arms.

 

I think I've isolated the source of the noise. I described the noise somewhat inaccurately in my original post. After listening closely, the noise sounded more like a rock or something else rattling against metal. It's coming from the catalytic converter. I noticed the noise only happens when I'm coasting in gear, and only when the engine's warm. It never happens when I'm running under power (i.e., with gas pedal depressed). I was able to reproduced the noise by revving the engine, with the car not moving. The noise happened when I released the gas pedal during revving. I listened with a mechanic's stethoscope, and determined noise was coming from the converter. I've attached two sound files with the noise: one is while revving the engine with the car not moving, and the other while coasting downhill in gear. Please listen (note - the original files of the recordings have a ".m4a" file extension. The system won't let me attach this file type, so I renamed it with file extension ".txt" Please rename back to ".m4a" after download before playing. Sorry, that's the only way I could get the sound files to upload. If anyone have of an easier way, please let me know - thanks).

Does anyone have a speculation on what's going on with the converter? Should it be replaced? I was thinking by removing the converter to see if I can shake out whatever that's loose inside.

 

 

I don't think I heard backfire. Also, the engine runs smoothly, and the manual transmission shifts without problems.

I removed the converter and shook it by hand. It made a rattling noise liked there are small pebbles inside. I've attached a sound file of this (note - please rename file to ".m4a" extension as before); please listen. The mesh on both ends of the converter keeps what's loose inside from coming out.

The rattling sound from the removed converter isn't all that pronounce, which makes me wonder whether this is the only sound I'm hearing while the car's moving. I'm pretty sure this is the only sound source when the engine's being revved while the car's not moving, but I'll listen with the stethoscope again before investing in a new converter.

 

 

I'm in NJ and the car no longer requires emission inspection, so was actually thinking about doing what you've suggested. A Walker after-market converter is only around $100 or so. There are these high-flow converters, which I think are just test pipes, being sold on Ebay for around $30. Will installing a test pipe make the exhaust system much louder than the stock converter?

 

It will likely make it a bit louder and you probably wont notice any performance gains. But you'll never have to deal with a plugged up cat (trust me, PIA and it will leave you stranded). I had a not-so-reputable local muffler shop remove mine and weld a pipe in its place. They kept the old cat and didn't charge me any money.