When revving engine in Park, to a relative hi rev, engine generates repetitive hesitation action. Acts almost like a machine gun. Check engine light has come on, but is now out.

Engine seems to idle okay, with no hesitation, even with some acceleration appears to be okay. But, for now, the problem occurs at hi rev.

When driving there maybe an occasional hesitation, but not always.

Anyone have any thoughts as to what may be causing this?

fuel pressure/delivery problems are common causes for "at speed" performance issues.

change your fuel filter and try running some fuel injector cleaner through your gas tank.

That description is very difficult to understand from a distance(kinda like when a friend sayd their car goes ooOO-Whee-Ooo or whatever), but
it sounds like you are missing on one cylinder. I looked at another Buick that made a similar sound recently, and it turned out to be a bent valve. Hopefully yours is something similar like a plug, wire, or coil that can be replaced.

-Bob C.

When you rev your engine in park it will shut off fuel to the eng. ( this is normal and was programed into the computer to protect the eng. with a built in rev limiter ) .
If you have a miss at high speed a scan tool will show what cyl. it is . most common is plug wire and sparkplug or coil pack . HTH
John

I will first start by changing fuel filter and adding inj. cleaner.

Sorry i didn't read this sooner. Are you sure you're not "up against the rev limiter? I'm not sure that engine has one, but i'm pretty sure. That's exactly how a limiter sounds. If that's the case everything is normal. The only time you would experience this while driving would be at the cars top speed. EXAMPLE: 1994 caprice w/LT-1(civilian) is limited at (i believe) 114mph, same car in 9C-1 (police )trim, the limiter is set at (i believe) 139 mph. check my facts at the Impala SS forum. Miles