Long time-no post, but my '98 has been making an odd noise for about a month or two now, and I really can't seem to place it.

It started one snowy day, pulling out of work. Out of nowhere, there was a buzzing at low speed while accelerating. Seems to be coming from the Driver'* side engine/transmission area. It comes and goes, not all that consistent. It does mostly do it at low speed, while accelerating, but it will also sometimes make the noise, more quietly, at a steady state speed. Rarely it has done it at idle, in park. Sadly I was not under the hood at the time though.

I should also note that the vibration/buzzing changes in speed to match the engine RPM.

It almost sounds like a heat shield vibrating against something. While I haven't been under the care in a while due to the crappy Michigan winter, I don't think it'* actually a heat shield. Too dependent on engine load and RPM, I think.

A quick look under the hood showed nothing out of place.

I'm wondering if it might be something inside of the bellhousing area, or the torque converter. Do they ever make a noise like that?

As always, any thoughts are appreciated.

I would still vote for the Cat Heat Shield. I would put the car up on some ramps and start the car up in the morning when the engine is COLD. You should be able to better locate the source then,

sorry accidental post

My manifold shield came apart at the welds and was doing that, it actually dropped an inch and was just sitting there.

i have a rattle/ buzzing too that seems to be coming from under the hood, im almost positive it is a heat shield and i will be looking into it shortly, but my guess is that that is your problem.

I'd check the heat shield on the 'cat' too. Mine lost a few tack welds (on the truck) and I drilled it through the flange and stuck a #10 screw through it with a split washer and double nuts. It lasted nearly two years before it wiggled loose again. The gap between metal pieces doesnot have to be very big for it to rattle.

Sorry to start a topic and seemingly abandon it, but I got sick, got busy, and just now finally got back to reading responses.

Thanks to all who did respond...

I can rule out the heat shield on the cat itself. That fell off a couple years ago. I don't park over dry leaves anymore...

As for the heat shield above the cat though, I will have to check it the next warm day we get.

I do hope it'* just a heat shield! My gut was telling me that it was something more mechanical, but my guts have been off lately anyway. I just can't think of anything specific that would make that noise, other than a heat shield. Which would seem to argue for it BEING the heat shield, but it just sounds so ... not like a heat shield sometimes, I remain unconvinced that it is, until I'm able to crawl under there and see.

That said, my wife has been driving the car for the past few days, and she claims not to have heard any such noise. It'* been unseasonably warm, so maybe it'* slightly cold-related? Winter is back for this weekend, so I guess we shall see.

I'll update with what I find, when I find it.

Thanks again.

my rear manifold heatshield was broken at the welds and just sitting there making a rattle when sitting in the driveway idling and going down the road...

Well.... The noise is gone for now. Strange, but true.

I guess I'll just forget about it until/unless it comes back.

I love it when problems just go away.

Thanks again.