One problem related to engine grinding noise has been reported for the 1999 Lexus LS400. The most recently reported issues are listed below.
I am reporting this because it might provide a clue to the Toyota racing engine problem. On each of two days before I took my 1999 Lexus 400 to the dealer for repairs, the engine would race at an estimated 4,000+ rpms and emitted a grinding sound as the car was started. After turning off the engine with the key, the car would restart without a problem. Strangely, the dealer did not record this particular complaint, but stated that diagnosis revealed that starter was failing. I was charged $990 for replacement and repairs. I could not get a satisfactory answer as to why a faulty starter would cause the engine to race. I have driven the car over 10,000 miles since then without a problem.