Exhaust Buzzing/Rattle (??) - Honda Prelude Forum

KtrainHurricane · 11-07-2011, 08:27 PM

I had a shop piece together an exhaust setup for me a little bit ago. I went with a Vibrant 2.5" high-flow cat, Magnaflow 14" (body length) resonator, OBX twin-loop muffler, and 2.5" piping. I also have a CAI and stock header.

When the exhaust was first put on, I thought it was a little louder than I wanted, but sounded good overall and I was very happy. However, about 1-2 weeks after the install my check engine light came on. I hooked up the OBD scanner at Advance Auto Parts and it read the code for a bad cat. Then, shortly after that, I started to notice an EXTREMELY annoying buzzing/rattling sound, which only seems to happen between 1500-2000 RPMs under acceleration.

A friend of mine was telling me not to even put the high-flow cat on there in the first place, and to just go with a 2nd resonator if anything. He told me that the cat probably blew out already and thats why I got CEL. Upon doing some online research, it seems as though a blown cat can also cause the buzzing sound...but what is the likelihood of a Vibrant cat blowing out after only a week?!

Or do you think that it is actually the muffler and not the cat?

I was ready to buy a 2nd resonator and take it to a shop and have them replace the cat with it (and add non-foulers) but before I do that I want to be certain this will cause the problem, and not leave me spending money for no reason.

KtrainHurricane · 11-07-2011, 08:35 PM

Not sure whether or not this is important, but if I rev at idle I do not hear the buzzing...only when the car is actually in motion.

zfinatic · 11-07-2011, 09:35 PM

My civic did this...if you got clamps holding the exhaust pipe together they could have come loose and the pipe inside the other is what's rattling.....if your exhaust is welded its most likely your cat.

KtrainHurricane · 11-07-2011, 10:02 PM

^everything is welded.

And i have read a lot about the heat shield on the cat being loose...but would this cause it to rattle only between 1500-2000 RPM?

jkoni426 · 11-08-2011, 09:01 PM

for the buzzing exhaust: take it back to the shop that installed it and tell them to fix their s h i t ty job.

for the bad cat code: just do the spark plug non-fouler mod, it's an easy diy. if the cat's pretty new, the reason you're getting the code is the increased flow from the cat itself, not because it's bad. I have the same situation with my '96.

KtrainHurricane · 11-08-2011, 11:32 PM

Quote:

Originally Posted by jkoni426

for the buzzing exhaust: take it back to the shop that installed it and tell them to fix their s h i t ty job.

Well if the "buzzing" sound is caused by the cat or exhaust itself being blown out, then it would not be the shop's fault...right?

P.S. nice to see a fellow Ravens fan on here

jkoni426 · 11-09-2011, 06:55 AM

you could always tap on the cat to see if you hear a rattle there, but I'm assuming the buzzing is from an exhaust leak since you said the whole system is new. I would just take it back to the shop and get them to check for leaks.

KtrainHurricane · 11-14-2011, 07:54 PM

Ok so I took the car to a friend's shop who made some time to look at it on the lift for me. After banging around a little bit, he came to the conclusion that the flex pipe is causing the buzzing. He said it was splitting and breaking apart, and causing a harmonic vibration (which is why it only buzzes in a 500 RPM window).

So here is what I am looking at:
-replace flex pipe
-add second 14" resonator (to quiet it down a little)

Can anybody give insight as to how much this should cost (including the price of the resonator and new flex pipe + install for both)? I have received estimates from two places, but both seem to be much higher than I expected...