I got a 1998 Nissan Frontier 2 weeks ago. It has an auto tranny and
110K. It had the "Service Engine Soon" light on shortly after I got
it, and my mechanic fixed 2 items including the O2 sensor. The light
went away after that.

The engine seems loud - at least, louder than a 2.4 4 cylinder should
be. My mechanic has checked the truck out and has not found anything
obvious, including the exhaust system. It seems louder on startup and
for the first 2 minutes or so after starting, but never gets really
quiet. It's actually a buzzy sound (while driving, anyway), and this
buzz is transmitted to the cabin pretty strongly. This makes driving
the truck enough of a chore that I won't keep it if I can't find the
problem.

Anyone have any insights about this?

Thanks, Steve

Steve wrote:

sounded like it was knocking and going to blow up), but the sound went
away completely after warm-up. I took it to my mechanic, expecting the
worst, but he said the intake manifold was cracked, and when it heated
up, the crack would seal because of the expansion. A new intake
manifold fixed that problem for me.

Jim

Jim wrote:


Jim

"Steve" <secretariat73 (AT) yahoo (DOT) com> wrote

Probably a problem with an exhaust manifold...bad seal or a crack
somewhere...should be fairly easy to localize the sound.

Bobby

I just heard from my mechanic - it is, indeed, a cracked exhaust
manifold.

Good call, Jim & Bobby!

-Steven-