My 2003 Eclipse has an intermittent fault that occurs at speeds over 40 mph. It drops power, the tachometer drops down to zero, the engine is still running but the power decreases. I have been able to bring it back in the past by putting it in neutral, revving it, and slotting it back into fifth gear but my mechanic at the dealership can't work out what is causing this. This morning it happened twice, the first time I brought it back but the second time, which happened a few minutes later, I couldn't bring it back, then the engine stopped and I had to pull over and get it towed. Any ideas on what would cause this?