Bleakened

Stock automatic '98 Civic DX hatch with a D16Y7.

I've had a rasp that I absolutely cannot pinpoint. It only happens from about 2.6k to 3.5k RPM whether it's in drive in any gear or park/neutral. Only RPM dependent. Not speed.

Some affecting mods:

- Random ebay header
- Yonaka cat-back
- Random ebay CAI down to bumper

I've removed ALL heat shields and checked clearances of exhaust piping. Nothing hitting oil pan or anywhere else.

Sound is definitely being amplified by the exhaust. Very apparent that it's comin from the muffler and not anything on the body.

Past exhaust did the exact same thing with a completely different setup except the header. I've gone through like 4 mufflers that people have given me and now all new piping and it still persists.

YouTube videos of people with the EXACT same setup as me do not have this rasp problem.

So is it maybe my valves? Do I need a valve adjustment? Could it be the header? Header seems very solid with no cracks and some very hefty welds!

Sorry for the long post, any advice on what to try next would be great!

Tegra206

iTrader: (2)

did you inspect the header for cracks? I doubt it's the cause, but it's cool to eliminate things maybe haha

Bleakened

Yes, I completely removed it and looked it over and even had one of my friends who is a professional welder look it over and he said it was pretty damn solid.

Former User

Have a buddy rev the engine to rasp rpms. Does pressing the end of a length of 2x2 wood against any particular section of the exhaust system eliminate the rasp?

Bleakened

Would using a jack to apply some pressure work about the same?

Former User

Definitely raise car on jacks, if you can reproduce the noise like that. Apply pressure to exhaust pipes however you wish. I suggested a piece wood to avoid burning your hand on the hot exhaust pipe. And if the wood is long enough, crawling under the car may not be necessary.

Bleakened

A scissor jack on multiple points including header, muffler, resonater, test pipe and S pipe yielded no change at all in any way

Former User

The noise appears not to be due to vibration of the exhaust system.

Try pinpointing the noise source by raising the car on jack stands and crawling under with an engine stethoscope.

Bleakened

I'll go out and pick one up tomorrow and do just that. Any other suggestions until then?

zrxdarryl

Possibility: My 01 crv with yonaka cat-back was doing this until I noticed the header-to-cat donut gasket was gone. Replaced donut and rasp left the bldg.

Fnix

iTrader: (1)

If you have these bolts they could be loose.

RT_NEWYORK

Same thing happened on my em1's exhaust. I had a strange sound start around 3k rpm as well. When we got it up on the lift it was just one of those bolts showed in the above picture.

Bleakened

Nah, I have some regular stainless bolts with nylon locknuts and washers.

Also, I bought a stethoscope today and used it everywhere but all the noises only amplified when revved but didn't change... so in short I still couldn't locate the source.

A new development did happen though: when I switch into reverse and lightly tap the gas on and off I can hear something with a loose rattle. It will do it in drive too but far quieter. Maybe this is the rasp I'm getting when at 3k rpm? I can't locate it though, everything is tight underneath.

I have also noticed now that 1 of the bolts on my transmission brace (the one that goes over the dust shield) is not in all the way and appears to be cross-threaded as it won't turn in any further. Maybe it's this?

I'm all out of ideas.

Bleakened

Okay, I came back to say that my problem has been solved.

I hate when people don't come back and say what they did to fix a problem - people will find that old post looking for answers and find none!

I had a universal cat welded in just after the header downpipe and the rasp is 100% completely gone. One smooth, even tone across my entire range from idle to redline now. Thanks guys!