What the heck IS this?

[Synned]

On my 95 I have the weirdest rattle coming from the engine bay...but heres the weird part...ONLY at 22-2500 rpms. I mean only..
Its like it just comes and disappears. I could see if it was random but I don't get what would rattle at a specific RPM? It only seems to do it under load...I think.

 

[Marlboro_Man]

Could be a heat shield rattling if you still have cats.

Might as well sell it and buy a fox

 

[sunil6784]

Mine rattles at that same RPM, but not from the engine bay. Mine sounds like its coming from the tranny area...I found out that its coming from the two upstream cats.

 

[Synned]

Mine rattles at that same RPM, but not from the engine bay. Mine sounds like its coming from the tranny area...I found out that its coming from the two upstream cats.

Alright, we will see when I replace my h-pipe. But I still dont get why it picks the RPM perfectly every time.

 

[HISSIN50]

Does the noise or range of RPM change depending upon how hard you stand on it?

 

[Synned]

No, the rpm is ALWAYS ~22-2500 never changes, and it doesnt matter how hard i push it.

 

[Daggar]

I second the heat shield... Also... there may be some portion of your exhaust that banging up against some other portion of the car. That's what I've got currently. Spot on for a specific rpm as well.

 

[tunedin302]

It's called frequency. When you exhaust hits a certain frequency (sounds like 22-25k) then it cause the heat shield to rattle. It's very similar to if you have ever seen cars with a decent set of subs and inadequate sound proofing. Certain parts of the car may rattle at certain sound frequencies but not others. I think a similar principle applies to your case. A quick test would be to take a set of pliers and bend a part of the heat shield slightly. This will change the freqency required to make it vibrate (rattle). Good luck.