Troubleshoot?

I own a 1998 Acura SLX, which is practically identical to the Isuzu Trooper. I believe it was even manufactured by Isuzu. For the third time now in the past 5 months, I have had a starting problem. The battery and starter work fine; the engine cranks, it just won't turn over. The first time this happened (February), I took the car to my mechanic and he replaced a valve (not sure which one). For two months afterwards, it started fine, but then arounfd the end of April, the problem surfaced again. I had the car towed to an Acura dealer, but when the technician tried to start the car, the engine turned over! Since the car started, the dealer could not recreate the problem and found nothing wrong. Now, two months later, I'm having the same problem, and the engine won't turn over. Does anyone have any idea what the problem is and how to fix it?

my honda shifts too hard and sometimes too quick, what should I do?