This is sort of weird little issue. Why does my exhaust buzz once or twice when the car is accelerating after a cold start? It'll only do it in 1st gear @ around 1500RPM and no more than just a few times before stopping - I guess once it warms up even the slightest bit, it stops. It sounds like it's coming from the passenger side. I don't think it's rasp, either - it's a fairly pronounced metal-to-metal buzzing noise.

Any ideas?

 

Probably the simplest explanation and I'm sure you've already checked, but are you sure the exhaust is fitting properly? Maybe it's loose and the vibration caused at 1500 rpm is causing it to buzz against something.

 

Everything seems really snug and tight. But the car will go back on a lift this Thursday, so we'll see.

 

+1

Used exhausts need a little more attention when installed.

Just go back under the car with a wrench and that should fix it.

EDIT: when you are under the car make sure the exhaust is fully cooled before you work on it. Try rapping on several points along the length of the exhaust to see if you can find or isolate any rattle spots.

 

Thanks, Hydra.

It's just weird that it only does it once or twice and then stops.

 

Expansion of a slip joint when heated?

 

I'll have my shop look into that.

Thanks again, man. =)

 

check clearance of rear under strut bar and your differential housing. I had rattle issues with my Borla around that area. Only when cold also, i guess the pipes were flexxing just enough to tap the strut and cause vibration at certain RPMS. You can tweek the exhaust hangers slightly to improve clearance.

 

Will make mention of that too. That could be it.

 

i forgot to mention another rattle issue i had that is near impossible to find. The furthest rear hanger coming off the car was vibrating against the hanger on the exhaust. The hanger on the exhaust slides through a rubber mount that is connected to the car by a metal bracket. When my exhaust hanger slid through the plastic mount it was angled poorly and was pressing up against the metal bracket that attaches the hanger to the car. I had to grind down the center of the cars metal bracket so the hanger on the exhaust wouldn't press up against it. Took me 3 weeks to find that one, unlikely it is the same thing but if you absolutley can not find any other touching points, try that one. It's a middle hanger towards the back, good luck with things.

 

Thanks, HK. I'm going to print the responses out and bring them down to my shop.

 

Keep in mind that when the car is on the lift, it will have much more clearance to the sway bar as the weight of the wheels pulls the suspension down. I betcha it's a passenger side sway bar clearance issue as mentioned above.

 

I frigin love this forum. =)

 

my invidia G200 does this. I get alot of buzz/rasp when its cold but after warms up for a minute it goes away.

it's normal as far as i know. Basically just the types of metals and the way the exhaust is designed.

 

Nah, it's definitely rubbing on something, since it's only coming from one side.

 

I HAD THIS TOO! A shop i go to solved it when Riverside Infiniti could not, its the rubber hangers starting to give out. They are allowing the exhaust to move under load and rub on the center frame brace. The rubber hangers seem to be tight and not giving out when up on a lift but stock rubbers cant handle an aftermarket exhausts weight or odd shapes for long.

I have a g35 so it may just be on the G car but i doubt it. theres a metal brace thats bolts about in the middle that connects the frame rails. My shop installed a stiffer aftermarket rubber mount in the area and it was solved.

Hope this helps.

 

Oh, it was fixed. It was the EVAP canister. It was relocated and no more buzz. =)