I have a catless EVO 9.... When I start the car and its cold I get that nasty sound like it has an exhaust leak.

I've even gone back to my stock exhaust (catless) and the same noise is present so its not a leak. Wideband reads normal afrs. The sound can be heard exiting the muffler.

Once the car has warmed up the sound is completely gone and it just purrs.

Does anyone else have this? Could it be caused by cold start ignition retard? Any other explanation for it?

 

not my evo but my DD 05 4.7 Jeep has a leak from the exhaust manifold, it goes away when hot too, metal expands and seals shut.
something is not tight

by the way you posted in the wrong place

 

What do you mean I posted in the wrong place.... I suspect this is a tune issue with cold start timing retard. Curious if anyone else has the same issue.

 

I have the same issue. It started right after i changed my blitz downpipe to DCsports. But I still think its an exhaust leak, because after some time the sound became louder and my WB started to show leaner...((

 

lol its pretty heavy and sounds nasty! i got a 3" TBE no leaks (at least i think so)

if u want i can try a video or u can post one i will let you know if its identical. in terms of the ignition warm up retard just use periphery bits to disable.


i may give it a try this weekend!

 

Maybe you do have a leak. Sometimes the leaks seal up when hot.

 

I had a simular issue with my megan DP....the flex section would leak like crazy until it was warm. Then the issue would be gone.

I replaced the DP with a new one without the flex section and put in a new doughnut gasket and flange gasket at the end of the DP....problem solved.

While I was at it I wrapped the entire DP with DEI header wrap and sprayed it with DEI high temp silicon spray. The end result is a slightly quieter exhast tone and maybe a smidge better spool from the heat being maintained in the exhaust causing faster exhaust flow.

 

I had the same problem... poorly lapped flange on the exhaust. When I changed the piece the non-flat piece had warped the one next to it. You can possibly double up a gasket to help... but that is not recommended.

Did your gaskets have burn marks on them past the pipe area?

 

I have a leaky flex section that's causing similar problems.

You could always use the trick of running a little bit of Seafoam in through one of your vacuum ports. As that stuff burns, it smokes. You'll be able to see even the tiniest of exhaust leaks.
It also does a decent job of cleaning out your combustion chamber. You'll want to pull your plugs and clean them afterwards. It's also suggested that you change your oil, so do it before a regular oil change.

If you have a WB sensor, I'd pull it out before doing this. This may have caused my last sensor to die.