2 problems...ehxaust and under hood noise

[Tx-Sx-FS]

i need to know that when i accelerate..the engine or something under the hood makes a rattling noise...i think its the fan but i have no clue...all around the fan where it connects to the pulley its cracked about an inch...so could it be that? also when i left off the gas and let the engine slow me down..the exhaust sounds like there is air being trapped inside and like bobbles...im thinking that its the CAT..i took off all heat shields so its not those...but if its not the CAT then could it be that there is an air leak or a hole from when i put a tip on the exhaust that there is a hole? well any help would be appreciated..thanks

[knowleqe]

the rattling noise COULD be your heat shield on the exhaust manifold. as for the bubble noise, it sounds like backfire, try a search and see what you get

[NisMoSilEiGhTy]

the rattling noise is most likely your heat shield, i just took mine off you dont need it....secondly the exhaust noise is prolly the cat or it could just be like in my case...an extreme case of carbon buildup....seafoam the crap outa it and see if the noise goes away

[Tx-Sx-FS]

yea ima do that seafoam to all 3 parts sometime this weekend prolly...do i need to replace 02 sensors? or is it just incase??

[DrIfT_FoReVeR]

i used to have that sound under my hood when my RPM's got up to about 3000, and then anything after that, it would stop. so i opened the hood and played with the throttle body and revved it until i located the source of the sound, and it was the exhaust manifold shroud/heatshield. the welding had either broken off or warped off of one side, so i just shoved a 6 inch gutter nail in there to fill in the hole until i got a new exhaust heat shield from nissan.

this is only a temp fix, but it does work and it wont sacrifice performance...one bit of advice though, don't use anything made out of plastic or wood...bad news...

[NisMoSilEiGhTy]

u should only have one O2 sensor on the exhuast manifold but u dont have to change the O2 sensors AND sparkpugs!. also its a good idea to change your oil as well afterwards. u have to change everything b/c they will become carbon fouled and will be useless after u see foam it. the nissan sparkplugs are $3 and the O@ sensor is $70 if u get it through nissan.