civic idle and exhaust

HONDA CIVIC
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JAB
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1997 civic ex d16y8 85516 miles. Just recently I took an aftermarket racing muffler off the civic the new muffler is a bosal stock aftermarket. The exhaust system still sounds loud like the racing mufflller .
I contacted the company the muffler came fom they said it meets stock specs and should be quiet.
Also the car idles around 100 and 200 rpm when warmed up the air conditioner has to be turned on when stopped at red lights so the rpm goes to normal if not the car sounds really loud and accelerates slow. Ther are some external modifications on the car like lighter underdrive pulleys , cool air intake I wonder if the cool air intake is causing this problem.

Does anybody have an idea of whats going on?
Jul 20, 2007 at 2:40 PM
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JAB
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Also the check engine light stays on the car was put on a diagnostics machine and it shows no problems.
Jul 20, 2007 at 2:42 PM
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BPRICE443
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Was the muffler the only modification to the exhaust. Or did the racing muffler come with new piping?
Jul 22, 2007 at 11:21 PM
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JAB
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The muffler was the only change on the exhaust.
Jul 26, 2007 at 12:47 PM
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JAB
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The muffler was the only change no extra piping.
Jul 26, 2007 at 12:50 PM
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BRUCE HUNT
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I recommend the rag test as I call it. Cover the end of the tailpipe with a big rag and see what else shows up. You might find a leak along the system as you follow the exhaust forward. I own a bunch of Hondas and I have that same car. There is a problem on the exhaust manifold where the exhaust port pipes join together. I would check to see if yours is cracked. That can greatly affect the way the system runs. Take off the pretty cover and look at it. The rag test should lead you up to this spot. If it is as I suspect, you can replace with new or used or I just welded in back up.
Jul 26, 2007 at 12:55 PM
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KIN CHAN
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Jul 26, 2007 at 1:31 PM
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JAB
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Sorry for taking so long to get back. I took off the exhaust manifold cover and right in front of my face was a crack 3 inches long. Thanks Bruce.
Ive got an old aftermarket header sitting around I bought it five years ago and never installed it.
Thanks for the help Ill donate some money.

One more question too Bruce or anybody .Can I splice and add an extra two feet of wire to the o2 harness ?
The aftermarket headers o2 harness is short ,has too be rerouted so it will go to the sensor hole near the catylitic converter Id hate to go spend thirty dollars on a extra o2 sensor extension harness ,they are hard to find.
Aug 11, 2007 at 1:12 AM