The most probable cause is poor fuel or water in your fuel. This could also be due to the timing being out of proper adjustment.
It is the alternator....
what kind of noise?
Muffler
Most likely needs a tuneup done. Check the timing and change the normal tuneup part.
a lifter
Bad ignition coil
The most common cause is slipping belt
you have a control vacuum leak, listen for hissing noise under dash when engine is running.
With out hearing it, It is hard to say whats wrong. But the most common noise like that would probley be a ROD knocking. Time for engine overhaul.
If the 1999 Suburban noise is a sort of loud banging noise, the problem could be that the engine have jumped time. Jumping time would cause the noise and jerking in the engine.
could be a center support bearing or a bad engine mount. i would check those first.
its amazing