Larnach

Hey guys.

I would just like to know why this goes on. When the car is cold, or its just been idling, if I get on it leavin my house or anywhere for that matter, it sounds like a hill billy truck, like glass packs, then after it does that and its "cleaned" out it has a real nice tone to it afterwards. I have stock manifolds, cat, and an open exhaust, any thoughts? Is there some valve that opens and closes in the exhaust manifold?

Thanks

cop01

I have the exact same exhaust setup and sound.... and it happens about 3k dosnt it? from my simple little mind, ive come up with: the wavelength of the sound going through the shrunken (cold, metal expands when its cold but you knew that im just gonna shut up now) pipe has a different wavelength as when its heated up and expanded. ive hooked my car up to a scanner to prove this and nothing is different from when the car does that to when it is warmed up and dosnt make that sound. so I would bet the farm that theres nothing wrong with your car (sorry if this is unclear but Im pretty tired, anyways I hope this helps)

93Z286Speed

mine does it too.. its louder and less nice sounding when its real cold.. let her warm up and she sounds great gotta be with the expansion of the warm metal (well contraction of the cold metal i guess)

Larnach

Thanks for the responses, the only thing is though, is that it will do it even if I let the car warm up for about 5 minutes, but as soon as I "clear it out" by flooring it through 1 and into 2nd, it sounds fine, even if the engine is still relatively cold. I dunno, maybe the exhaust heat from flooring it super heats the pipe.

Thanks again.

Larnach

My temp was at 180 yesterday after driving for about 30 minutes, it didn't make the sound till I was just sitting at idle at stoplight after stoplight, then when I floored it... cack! cack! cack! Clogged cat you think?

cop01

hmmmm, thats interesting, myabe your right and it is a clogged cat....... do you have any codes? does it go into open loop mode out of the blue?

Raped Ape

I've always heard that a clogged cat will glow. Maybe you could look under the car tonight to see if it is glowing. Can't hurt anything (well, unless you have a bad back ).

Larnach

Thanks guys, do you think the pressure from the exhaust is pushing that "peice" of honeycomb up against something, then when its at rest, the vibration from the engine/exhaust assembly kinda vibrates it in the way again?

I should just replace the convertor anyway, 116,000 miles on it... hell the opti lasted 110,000!

joeSS97

Just a thought,maybe you are running too rich.Thats why it changes when you clear it.

Larnach

There's a good chance that it is running rich, I descreened the MAF and got an open exhaust at the same time. Only problem is I lost my MAF screen and ring So I can't "re"screen it.