My car will turn over but then kills right away.low oil pressure

Well when your computer sees that the oil pressure is too low it will shut the fuel pump down as a safety precaution. What could be causing the low oil pressure could be a few things. You could just be low on oil (5 qts is standard on most vehicles), your piston rings could be going bad causing you to lose compression, your head/valve cover gaskets could be breaking down which could cause you to lose compression, and your valves could be covered in carbon build up and not seating completely.  Try this; put a quart of oil in and try running some 44k power enhancer through your engine. If you are still getting the low pressure light it could be a mechanical problem such as your rings, gaskets, Etc.
The high idle could be a number of things. Your Throttle cable could be adjusted a little short, your Engine Coolant Temp sensor could be constantly reading that your engine is cold which would then dump more fuel into your cylinders. Your O2 sensor could be going out therefore constantly reading that there is too much oxygen in your exhaust and telling your computer to dump more fuel into the engine. Its a long shot but you may also have a timing problem.... Good luck and if there is naything else I can help with just let me know...