I recently replaced my 1998 Honda Odyssey cat converter after the emission fail. I think the guy who replaced it left some gap between the front side of cat and exhaust pipe. Now it is making sound as if muffler has a hole. I had someone check to see where the noise was coming from but he says its coming from rear joint side of cat converter with exhaust pipe.

1. How do I actually check myself where the noise is coming from? Is there a DIY way to check?

2. Since the cat has been changed, van's idle is not stable, sometimes its okay but then mostly when I stop at a stop light, I see idle RPM going up and down and it feels like car is breathing in and out. I am really confused. It all happened after the cat was changed.

3. Van is running heavy after new cat was changed and sometimes I smell something burning

I thought the mechanic probably left some bolts loose which could be tightened but all these other issues are baffling me. Car was running fine before this cat replacement except for the P0420 code.

Please advise

Thanks.

 

Go back and have them make it right.

 

It was through a mechanic who isnt available now and that's the reason I posted issue here else I wouldn't.

 

Then describe your situation in more detail. Can you not jack the van and go underneath it with your eyes and ears to see and hear where the leak is?

 

Sure I got a set of eyes and a set of ears and good thing you reminded me that they can be used for those. Its really a smart way to tell people how to approach the issue

. But at the same time I dont get under the car because of not having a strong jack. Sometimes the leak is not easily detectable.

I found the leak but rpm is not stable and it is still going up and down and car is still running heavy with extreme gas consumption and shutting off at stop sign of lights. It only happens mostly when car is run for at least few mins or miles. Cold car is little better than when it gets hot.