GM-GMC: Grinding on Acceleration, fan clutch, catalytic converters

Question
1993 S-10, 4.3L V6 with automatic transmission.  160,000 miles.

Well...I used to think this problem was only linked to my startup in the winter...but after some new pulleys & 100 degree weather, it started happening again...here's the deal...

When I'm in the truck & I'm running my A/C, naturally the truck doesn't accelerate as it should. When I accelerate, the truck sounds really loud...then I start hearing this grinding noise.

If I turn off the A/C & accelerate real slow (to bring the temp of the engine down), it doesn't make the sound anymore.

Also, I started up my truck this morning & it started making the grinding noise on acceleration.  I had to restart my truck several times before it would stop.  Once it stops, the truck runs perfect.

One last thing, I do know that my muffler needs to be replaced.  I know for a fact that the muffler is not making the sound.  But, could the engine have problems with getting rid of hot air b/c of a bad muffler?  

Thanks!

Answer
Usually, the muffler is not at fault unless it has collapsed internally.  The vehicle would run bad all the time.  GM has had problems with catalytic converters over the years, so be sure and have yours checked.

It is also possible that the cooling fan clutch is causing problems.  It can reduce power output significantly if it malfunctions.

You amy also have an accessory drive (alternator, power steering, A/C compressor, and/or belt tensioner) with a bad bearing.

I would have all of the above checked.