# Car Trouble

1. Jul 30, 2006

### Gokul43201

Staff Emeritus
Murphy finally got to my car! :grumpy:

I own a 1992 Honda Accord DX (160K mi on it) that's been running fine until a couple days ago.

1. Now, when I start the car, for about the first half a second or less - as the engine comes to life - there's a rattling sound that I hear from the rear of the car. I'm fairly certain it's coming from the muffler or its vicinity.

2. During regular driving, this rattle is not heard again, unless I'm driving very slowly (<15mph) over a bumpy stretch, or if I do a not-so-smooth gear change at low gears. Makes me think something not too light (something bigger than a washer, small nut/bolt or chunk of rust) is loose in the muffler.

3. Another sound I hear is a low amplitude, medium pitch hum, or rumble, coming from about the same location that lasts for about a second or two in the lower gears (1 & 2). I do not hear it beyond about about 1500RPM (which is pretty low for a Honda). I do not hear this sound at all if my windows are up, or if I have the radio playing (so it's not terribly loud...but then, it's a Honda - the engine itself is as loud as a grumpy lion).

4. I think both sounds started appearing simultaneously, and neither is audible from the 3rd gear and up - not even when I floor the pedal on 4th or 5th (but the humming sound may just be getting drowned out by ambients).

5. Now, from a cursory inspection of of the muffler, I have the following to report:

i) The muffler is fairly rusted near all the weld joints on the inlet side.

ii) Shaking the muffler horizontally (by hand, so amplitudes were small - much less than an inch), made sound like there was a lot of loose rust chips on the inside. It was perhaps a rustling kind of sound. No clanging or rattling - but then, I didn't really thwack it up or down.

iii) The back plate of the muffler (I'll attach a crude diagram, if I can) had an outward bulge in the small portion just below the outlet pipe.

6. That last observation suggests to me that there may have been an engine backfire or some similar weirdness that caused this. However, if the engine did backfire, I didn't hear it. On the other hand, I don't think I've ever heard an engine backfiring in real life, so I'm not exactly sure what it would sound like. But the engine backfire theory is a little weak due to the observation in point #4 - or so I think.

So, what do you experts think may be the trouble? Any ideas or suggestions or questions? Should I go do an engine diagnostic? I don't have either the expertise nor the time to do anything more than rudimentary stuff myself, but I'd like to have an idea of the possibilities before taking the car to a mechanic.

HELP!!!

Last edited: Jul 30, 2006
2. Jul 30, 2006

### Cyrus

Sounds like a loose muffler, have it bolted down to the car. Engine backfire goes POP.

3. Jul 30, 2006

### Gokul43201

Staff Emeritus
Last edited by a moderator: May 2, 2017
4. Jul 30, 2006

### Gokul43201

Staff Emeritus
Cyrus, I don't think the muffler itself is loose. I would have been able to shake it about if it was.

5. Jul 30, 2006

### Staff: Mentor

Sounds like it's time to get a new muffler.

6. Jul 30, 2006

### Gokul43201

Staff Emeritus
I do plan to get a new muffler, but I'm not sure if that's the first thing I should be doing. I don't want to change out the muffler before I know there isn't something else more fundamentally wrong - like an engine problem or a leak in the exhaust system. If that is the case, I might end up blowing out a new muffler from a recurrence of the real problem.

7. Jul 30, 2006

### Staff: Mentor

Do you know a reliable place that will check out the car and not rip you off?

8. Jul 30, 2006

### Gokul43201

Staff Emeritus
Not really. That's the downside of having a well-behaved car - you don't develop intimate relationships with mechanics!

But then, what exactly is a rip-off? For a poor, struggling grad student like me, even a cautionary diagnostic that runs up $100 is something I need to think about before jumping into. 9. Jul 30, 2006 ### wolram Ok, so are there any other symyoms? over heating, oil pressure light does not go out for some time time, engine using oil, have you changed gas stations, detonation is gas related, engine probleme are usualy rhythmic, ie a noise is either there at at certain rpm or conditions under load if none of the above change your (cylencer) :tongue2: 10. Jul 30, 2006 ### Gokul43201 Staff Emeritus Nothing that I can obviously tell. I'm not really loyal to a particular brand. I fill up whenever I'm low and I pass a gas station with a name that's familiar. Are you saying you concur that there has been detonation because of your independent evaluation of the picture or are you just going by my guess? 11. Jul 30, 2006 ### wolram You must be methodical when looking for noises on autos, the main criteria is performance, is your car doing what it should do, if it is perfoming as usual , you can forget engine problems, (tentiavaly) you must note any anomaly, if there are none then , look for ancilaray problems. 12. Jul 30, 2006 ### rocketboy My dad used to own a '93 Acura Integra, before we got rid of it it had almost 300k (km) on it. We experienced a similar rattling coming from the rear of the car, however for us it was the muffler loose and the sound came from the vibrating parts. It may be something rattling inside the muffler, have you ever replaced it before or is it the stock part? (the muffler system I mean) 13. Jul 30, 2006 ### Gokul43201 Staff Emeritus Wollie: Other than the sounds, I can't tell any difference in the performance. Rockie : I've only owned this car for the last 25-30K mi (abt 5 yrs). The muffler is not the original Honda muffler though. I guess right now, I'll just change the muffler and see if that stops the sounds...and take it from there. With the warranty that comes with the muffler, if I do have to change it again, it'll only cost me labor ~$25 or so.

14. Jul 30, 2006

### chroot

Staff Emeritus
Drive it until something actually falls off. Then, stop the car, identify the piece that fell off, and stop by the store to buy a new one.

- Warren

15. Jul 30, 2006

### Danger

16. Jul 30, 2006

### Moonbear

Staff Emeritus
You're going to make him wait until something falls off? Geez, you could at least tell him how to temporarily stop hearing the noise...turn up the volume on the radio!

When the neighbors start giving you evil stares as you drive by, you'll know for certain it's the muffler that needs replacing.

17. Jul 30, 2006

### Gokul43201

Staff Emeritus
Smartass, Danger. Build me a car for \$10K and give me an a 100K mile warranty on the drivetrain and engine and you've got a deal.

18. Jul 30, 2006

### Staff: Mentor

What kills me is seeing someone driving down the road with their muffler dragging and showering sparks. Can they not hear that???

19. Jul 30, 2006

### edward

A few things you can look for: Make sure that the exhaust pipe or tail pipe are not coming into contact with anything. If this should be the case some new muffler hangars would stop the rattle.

You can usually tell if the rattle is coming from inside the muffler by tapping it with a rubber hammer or block of wood. Tap on the lip (on the end) because the metal is thicker there.

You may also want to look at the catalytic converter. Most of them have a heat shield that can come loose.

20. Jul 31, 2006

### NoTime

A good car stereo will fix that :rofl: