you must smell raw fuel coming out of the exhaust too right? you problem most likely is the ignition coil is bad. i had the same problem with my sc400. in the morining the car started up fine, and i drove out of the driveway and got out of the car to go put mail in the mail box. and when i got back in the idle was rough and when i gave gas the tach dropped to zero and it sounded as if the car was running on half the cylinders. and they were. changed plugs, wires, cap, and rotor, that didnt fix the problem so i swapped out coils from my LS and it ran perfectly, so i found that the secondary coil was out. was 80 bucks at the dealer.