We just got this runner, and it is in GREAT condition.

a 97, 4X4 3.4 litre, SR5, desert dune color with rare factory polished wheels,
a VERY sharp 4runner. 83K miles.

It runs great, but seems to make a loud buzzing like noise between 2500 and 3000 RPM. Sounds like a heat shield or something like that. Anyone have any idea? Its kind of like the engine gets loud during this RPM period, but step on it.. and it downshifts and the motor pulls hard at the higher RPM of course, and the buzzing like noise is gone. (untill it upshifts again and puts it back into that RPM range)

Thanks for any help, guys.

 

Did you pull off the skid plate and have a look?
You might try that and inspect the exhaust for any loose parts which might be free to vibrate.
It could also be that the catylist in your converter is loose and causing the noise (if so, you need to replace it).

 

I have a 97 right now with high miles (197K). The previous owner has all the receipts since about 30K miles. As I glanced through them, I noticed that he had the same complaint at almost every service interval. Repeatedly the dealer noted "Customer complains about buzzing sound between 2500 and 3000 RPM. No assignable cause found at this time." At around 150K miles, the dealer notes they found a heat shield rattling and tightened it up.

A great way to narrow down a rattle is to get under the vehicle with a rubber mallet and lightly tap in different areas. Eventually the rattle will reveal itself and you can at least narrow it down to a certain area. Be sure to tap along the exhaust piping too.

 

The 3.4 engine has a buzzy resonance period that is worst around 2700 rpm. It's just the nature of the beast - nothing you can do to fix it.

On our '98, I considered it no worse than mildly annoying, but you may percieve it differently.

Take comfort from the fact that the 3.4 is turning out to be one of the most durable, trouble-free engines Toyota has ever built. Good luck with yours.

 

I HAVE THE SAME NOISE!

I think it is a heat shield, sometimes I hear a slight rattle when I close the passenger door, though it is not in the door

it seems the noise comes from the dash...and is at 2700 or so

I think it is the exhaust, or heat shield causing a slight vibration

I will check it out when I put my new differential in next week

 

I have exactly this issue. I think its between 2700-2900 RPM. I was wondering if maybe it was an exhaust vibration dampener or something, but haven't really inspected beyond that. It is less than a rattling as described elsewhere in the thread, buzzing is how I'd describe it.

I feel a little better knowing I'm not the only one that has noticed it. I bought mine with 59K, is it a known problem even from a new engine?

 

I had a 2000 3.4L with 18K miles and it never made this sound.

 

Mine has this too. However, my noise is a bad wheel bearing that I've been driving on for a few weeks. Ughh..

 

I guess I'd call it a "characteristic" rather than a "problem". I've ridden in and driven several 3rd gen 4Runners besides the '98 I owned. All had the buzzy resonance to a greater or lesser extent. My '98 had it when new and it never changed during the 5 years/75K miles I owned it. It could be that something like a heat shield also is loose and sympathetically vibrating on the original poster's truck - kinda hard to tell from his description.

This sort of thing isn't unusual. Our current '03 V8 4Runner has a mild case of the buzzies at very low engine speeds (<2,000 rpm), and our '05 M-B E320 CDI diesel has a doozy-a nasty basso profundo boom at about 1400 rpm, which fortunately occurs only in a very narrow rpm band. The only two vehicles I can remember being resonance-free were our 2000 BMW 528i (inline six) and a '94 Camry V6.