If you can locate the area of the grinding noise, that might help diagnose it. Could be many things, but timing belt and tensioner pulley come to mind for me. The timing belt tensioner pulleys have been known to come apart - could be affecting timing as well as creating the noise and some of the other symptoms.
Any dash lights, codes? Check peripheral rotating equipment (a.c. compressor, p.s. pump, alternator). What is battery voltage with engine running at around 2000 rpm (can measure at jump posts)? Damper pulley running straight (little to no wobble)? Could it be coming from under a valve cover (rocker mechanisms and rocker what’s can break and otherwise start failing)? A.C. compressor pulley bearing failed and pulley scraping compressor case?
Besides the start of the grinding noise, have symptoms been changing or getting worse?
Others may offer other ideas on possible causes and troubleshooting ideas.
'98 LXi - Later Concorde gages (black w/ chrome rings)/'99 LX - LHS gages (white) - HIR bulbs