Hyundai Repair: Elantra 97 hard start, crank shaft position sensor, throttle position sensor

Question
I have a 4 door 1.8 L 97 hyundai elantra.  I had a crank shaft position sensor failure.   i didn't use the o ring that came with the sensor since it seemed to keep the sensor from being close enough to the shaft.  So once i got that sensor in the car turned on, but has a bad idle.  the engine eventaully dies out while idling.  i drove the car 1000 miles to Montreal and New Jersey like that and it ran fine while on highway, just had to keep giving it so megas when i was idling.  i replaced the wires to the plugs, but still bad idle.  no check engine light.  about 120000 miles on the car.

Answer
If there's no o-ring on the crank sensor, it'll leak oil and may be too close to the sensor wheel.  I suspect that the reason for your installation issue is that the o-ring from the old sensor is still in the block.  If so, it'll be fine as long as the o-ring is in good condition.

As for the idling issue, there are many possible problems.  I'd primarily suspect the idle actuator or the throttle position sensor, especially if the engine is just running slowly or stalling but not misfiring.