^ I second the CPS^
The Crank Position Sensor is located behind the passengers side head where the block and bell housing meet. It's held in by 2 (8 or 10mm) bolts. It may be dirty or have a rust accumulation on it. Try cleaning it to see if it helps. It operates on a magnetic based signal as the flywheel turns.
Pull the CAI (Cold Air Intake) to get a little better access to it.