Exhaust making strange howling noise!!!!!

[turdbird]

Ok, probably about 1/3 times i start my 96 f150 4.9 with true duals, the left pipe has a higher pitched howling noise, its a steady tone whether i rev the truck up or not it just gets louder. It will do it for about 6 seconds and then stop. The truck doesnt run badly because of it, but i took her to autozone to get her scanned and they said that the oxy sensor on the first manifold bank has a slow response on startup. Is that what causes this strange noise, i dont even know how it would make it, it sounds much different from the engine. The right pipe doesn't do anything. thanks.

[Bear River]

The slow response could indicate a bad sensor, but if you have an exhaust leak, it could be creating a howling noise if it was located in just the wrong spot.

More likely however, you should add an X-pipe to your system to balance out the exhaust flow. That seems to resolve most abnormal noises.

[turdbird]

I know that its not an exhaust leak, its almost electronic sounding. It started about 2 years after i put the duals on.

[Bear River]

What kind of muffler do you have?

[turdbird]

none, just walker high flow cats, its really strange, comparable to the howl of a wolf literally. It just isnt a natural engine noise, and the boys at the exhaust shop dont know what it is.

[kens64]

Can you get a recording of the sound so we can hear it?

[Bear River]

Question, is there any chance the smog pump is still hooked up? I know your custom exhaust probably doesn't use the smog pump, but I suspect it could be possible that it could be involved. I don't know really, sounds like yours can be tough to pin down. My dad has a '92 E350 5.8L and when it is going between 35-45 mph under light acceleration, it develops a howling noise that sounds like someone blowing across the top of a bottle. We haven't isolated the source yet either.

[turdbird]

i just have the air tube from the cat going out into fresh air, but this pipe specifically comes out of the front 3 cylinders, which the oxy sensor that is going bad is in the manifold of those cylinders.

[Bear River]

See if plugging of that tube resolves the sound. Beyond that, I really don't know what to tell you. As I said, my dad's van makes a strange noise and we don't know where its coming from or what's causing it either.

[xlman]

definately plug the tubes on the cats. during decelleration vacume is created in the exhaust and any leak or open tube will draw fresh air in causing ignition of any unburnt exhaust. that gets things extreamly hot, especially in that area. that is where the dreaded " pop, bang, pop, bang" comes from when you let off the throttle.