today i started my car early in the morning and drove around for may be 20 minutes. i came home and as i was pulling in my parking spot i started hearing these noises from under my car. to be specific it was more like a loose pipe rattling but it was a metallic noise for sure. i waited for my car to cool off and got under it and saw nothing lose or nothing stuck underneath creating this metallic noise. i shook the entire exhaust system as hard as i could and saw or heard nothing. i started my car back up and the noise was gone. after about 10 min it came back again and it sounded as if it was inside one of the pipes on the exhaust, but very hard to tell where it came from.
what the hell is this noise that comes and goes? i was thinking that the only thing different in my car is that i have been putting amoco fuel at a different spot. could it be that i am not really buying 93 oct at that gas station?
i have thought that it could be knocking or detonation. i dont know.
can anyone give me any input as far as what it could be??? thanks alot

 

Do you have bullet mufflers? I do, and at 1900-2100 rpm's my exhaust sounds weird, almost farty. I've got Hooker LT's w/ an x pipe and bullets.

I thought it was my exhaust banging against something until I noticed it only happened at the same rpm every time. Could be a possibility, check next time it happens.

 

no i have flowtech afterburners and this is driving me insane. what exactly happens when you put a lower octane fuel in your car? i think that could be what is making that metallic sound inside my exhaust unless i have a flowtech muffler that is messed up inside.

 

Does it come from the back? Something I think happens is the heat shield rattles. Mine does it when my exhaust makes certain noises. I think I heard somebody say it has to do with the heat shield starting to vibrate at just the right frequency. Mine does it under part throttle sometimes, when it is cold outside, and when the AC is on. It comes and goes. Pisses me off though. Some people have stuck pieces of heater hose in there to keep it from being able to vibrate so much. I haven't decided what I am going to do yet.

 

Yep, same thing with mine. It's the heat shields... I have yet to decide what I'm going to do as well... since it's very easily accessable now that I have my entire engine compartment clear... mostly. Stick it out til we all figure out something that works thats not a ghetto-rig type fashion (like he said some people do with the heater hose) or just use the heater hose if it's that annoying... (which it could be if you drove it daily).

 

Yeah my exhaust hit the hit shield too. Only did it at certain rpms. I retightened all my exhaust clamps and then bent the heat shield just a hair with a pair of pliers. no more problems