My civic has been treating me great until about six months ago.  About
that time it started with this strange grumbly whining sound whenever
it was in gear and driving, mostly when accelerating.  About a month
ago, I noticed that I had a very small range of accelerator-pedal
motion in which I could accelerate.  If I pushed the pedal past that,
the engine just revved like it would if the clutch pedal were
depressed.  About that time I noticed that the grumbly whining sound
went away.  Since then, on only one occasion, the grumbly sound
returned and my acceleration returned to normal.

So, basically, it takes me about 20 seconds to get to 60mph from zero,
and I have a hard time getting much past 70mph on the highway.  The
engine is running fine, the issue is that it seems that not much power
is getting to the wheels.  Can anybody help me?

Thanks,

Nate