low exhaust-area rattle at idle... can't pinpoint it

[TheNorthWaves]

I didn't want to bother posting this, but the noise keeps showing up and bothering the heck out of me.

I never have my digital/video camera on hand when it happens either...

Basically I have a slightly rough idle (I have done everything in the book plus some, and it still exists, so I live with it) and it causes some kind of a low-pitched knocking rattle sound near the exhaust area. To be more precise imprecisely, it sounds like it's coming from the left side rear wheel area. This noise will just rattle on, sitting at idle in a parking lot. Thank god I have a girlfriend, I could never pick a girl up in this car right now!

Any ideas? I simply can't pinpoint it at all.

[Volf]

mounting bracket?

[Volf]

Heat shield?

[Estrl M3]

I had a sim ilar problem and actually found a hole in my pipe and a piece of metal was shaking around inside the hole causing an echo up and down the pipe.. welded the hole and no more noise..

kick or hit your exhaust piping while the car is OFF and see if you can hear the rattle..

[TheNorthWaves]

I had a sim ilar problem and actually found a hole in my pipe and a piece of metal was shaking around inside the hole causing an echo up and down the pipe.. welded the hole and no more noise..

kick or hit your exhaust piping while the car is OFF and see if you can hear the rattle..

I can't elicit the rattle by this method - it is literally only when the car is running. I've been underneath the car and hit everything in sight- nothing.

[rcM3]

i've got something simliar coming from the heat shielding around my mid-pipe. Its gone away since i've fixed my idle.

[bobbyp]

Could be the cats if they are original.

[Rob Levinson]

I think you should track down the source of your rough idle first. This itself is likely the complete cause of the rattle... and the rattle could be within the drivetrain itself!

If the rattle is only audible at idle, an engine or transmission sound could be what you are hearing. Some powertrain sounds are hard to pinpoint, and the under-car acoustics can make it sound like it's coming from somewhere else.

No matter what, look further into that rough idle. Whatever is causing it is probably also affecting performance and mpg.

[mmark.]

Perhaps a Loose baffle in the tail box if your muffler is OEM.

m

[bennyfizzle]

you don't have a lightweight flywheel do you? lol

[TheNorthWaves]

stock flywheel, etc... stock everything.

I wish I could fix the idle, but I have all but given up. Checked coils, replaced plugs, valve cover gaskets, cleaned ICV and replaced virtually every imaginable intake gasket, replaced all clamps with good ones and cleaned out all hoses, replaced all plastic clips/o-rings, cleaned MAF, tried both stock chip and dinan chip, inspected intake boot, replaced fuel filter. The only thing I have not done is actually replace the ICV and the intake manifold gaskets. I simply won't take all that stuff off until something underneath breaks (ie: starter, knock sensors). I was hoping a thorough ICV cleaning would do the trick - no such luck. Most of the things I have listed were done as routine maintenance along the way, and every time I've done something I've hoped that it would cure the idle issue. I'm stumped. I don't even think about it anymore...

[wmiranda]

Hmm,.. how about you start the car and if it's rattling at idle, get out and go to the back... either pushh the exhaust forward with your foot,.. slide a jack under it and see if lifting it helps... or using your foot, push is down.

I had a rattle and it was my exhaust tapping against a frame thingy (technical term) because it was so close (Borla).. couple of washers (SS of course) and the problem went away.

Your rough idle would be causing this as it causes the car to vibrate at a lower frequency and higher amplitude (as if you all didn't know).

Check you exhaust for leaks too... if there's one before the O2 sensors,.. you'll get erroneous readings at the ECU and this could be causing your issue.

Later!

Bill