The fact that this occurs after warmup (along with the sluggish, stuttering
performance) suggests the oxygen sensor may be near or is at complete
failure.

Most inexpensive source of OEM oxygen sensors I've found:
https://www.automedicsupply.com/

The grinding sound, though, suggests other possibilities as well.

www.autozone.com has a free online manual for your Prelude, for your
reference.


"Scythemk" <mikulevi@gmail.com> wrote
> Hi everyone,
> I have a 1993 Honda Prelude VTEC. I recently started having this
> problem where the engine pulls fairly well all the way up to, oh about
> 2200 rpm, and then it almost feels like a brake is being applied in the
> engine, the needle moves sluggishly and doesn't want to respond quickly
> to gas inputs. This lasts to about 3000-3500rpm and then it feels as if
> the engine lets loose again and the needle goes fine all the way to
> redline. In all these other rpms the engine feels fairly poised and
> smooth. However at 2.2 -3.5 k its just sluggish and sometimes the car
> even jerks a little under constant throttle and in gear. There is also
> a subdued grinding sound seemingly coming from under the car right
> under the gas pedal and an ugly note in the exhaust. This doesnt always
> happen but has been hapening more and more recently. My clutch was just
> recently replaced. I also noticed it does not do this when the engine
> is cold, say in the morning after leaving it over night. However once
> it gets up to operating temperature it starts doing it. One of my
> friends has suggested it might be the catalytic converter, as during a
> recent smog test i barely passed in the HC(hydrocarbon) category. Any
> insight, please?
>