Lawnmower sound under acceleration

[elgorey]

Hi guys,

I just picked up a 93 240, and it has a very coarse lawnmower sound whenever Im on the gas, but no sound when I am off. Not a regular rattling sound, the sound of a lawnmower engine is the best I can describe it. It seems to come from the drivers side of the engine bay.
I have done some searches, and none of the heatshield rattles, etc seem to fit it very well.
Anyone have any ideas as of what it could be?
Hopefully not motor related :(

thanks,
Evan

[Tyler Durdan]

Sounds like you may have a bad cat. Does it feel like there is back pressure on the engine (slow accleration)? Easy way to check the cat is to get under the car and tap it with a hammer gently. If you hear rattling inside cat, it needs to be replaced.

[fleaf]

I think you have the same problem I did...I posted this problem not too long ago.. but here is a link

http://www.zilvia.net/f/showthread.php?s=&threadid=25736

check the hose from your Air Intake Valve (AIV) into a pipe into the exhaust header. The hose might have popped off or it has ripped. If the hose is damaged, do not buy another rubber hose from autozone, pep boys, kragen, or home depot (I bought 3 different rubber hoses and all of them broke). You have to buy a "special" hose from Nissan that is able to withstand high degrees of heat. It cost 46$ which is a **** load but it will fix the problem. Or if you feel ghetto fabolous, just take the hose out alltogether and plug up the hole in the AIV. The only thing it does it help emissions. Come back and let us know...this problem doesn't seems like an uncommon one.

[240sxspeedracer1]

fleaf, when you fixed the problem, did the harley davidson type sound go away?
Come to think about it, I kind of hear a harley davidson type throaty sound but never thought about it until I read this post.

Also, if memory serves me correctly, there is a hose that comes from the intake, and goes to the aiv correct?> They say that this also doesn't need the hose and can be just plugged up. Are you talking about that one, I dont think you are cause you are reffering to a hose that goes from the aiv to the headers.

So basically, we can take off and plug up both of the holes where a hose should be connected: that goes to intake, and that goes to the headers, and the car should run fine except for the harley davidson sound coming from the engine? Is that the concensus?

[MyFirst240SX]

Mine made a sounds like that when one of my spark plug wires went bad.....

[fleaf]

Originally posted by 240sxspeedracer1
fleaf, when you fixed the problem, did the harley davidson type sound go away?
Come to think about it, I kind of hear a harley davidson type throaty sound but never thought about it until I read this post.

Also, if memory serves me correctly, there is a hose that comes from the intake, and goes to the aiv correct?> They say that this also doesn't need the hose and can be just plugged up. Are you talking about that one, I dont think you are cause you are reffering to a hose that goes from the aiv to the headers.

So basically, we can take off and plug up both of the holes where a hose should be connected: that goes to intake, and that goes to the headers, and the car should run fine except for the harley davidson sound coming from the engine? Is that the concensus?

yea sorry for the misundestanding. You don't really need an AIV at all, and you can just plug it up from the airbox like you said. You will need to weld it shut or get one damn good plug or else that thing will just pop off again and continue to make the same sounds.

Have you checked to see if the hose is ripped? Cause there can be other things that might be causing it to sound like that. eg. fuel injectors, sparkplug wires, etc...

[elgorey]

Thanks for the suggestions guys.

I dont think it was the cat, It is tight down there but I managed to tap it very lightly and couldnt hear any rattling.

I just inspected the AIV very closely, and what I found odd was that there is no rubber hose on mine. It is all metal and instead of going straight from the AIV box it goes towards the front of the car then loops back around to plug into the headers below the O2 sensor. I was comparing it to the pic that you posted in your thread fleaf. So that is odd, but im not sure if its the problem. (I wish I could take pics but its dark and rainy outside)

I noticed that one of the plug wires looked different, and loooked as though it wasnt even made for the car. So I ran out to autozone and got a new set of good wires, convinced that it would fix the problem. No go, didnt affect the problem one bit.

Another possibility that I am thinkis is that it could be an exhaust leak somewhere in the exhaust manifold/cat. I can smell the exhaust under the hood. Does this sound like a plausible scenario? Any other possibilities?

The guy I bought it from said he powerwashed the engine bay (:rolleyes: ) any possibility of water getting somewhere it shouldnt and causing it? (i would have thought that it would have burned off by now)

thanks guys,
Evan

[MyFirst240SX]

My exhuast one time due to hard driving or something broke off a bolt and started losing the bolts holding it on. My Car was real loud. might want to check that then.....

[SRKperformance]

could just be the noisy stock clutch fan

[the head]

i would say exaust leak start it and look for smoke under the hood or beneath the car you may need to have a friend rev the engine to find it though