It would cost $725 bucks
It has a variety of causes, most commonly a badly adjusted carburretor, or problems with the injectors. No way to tell cost of repair.
No, that has nothing to do with idle speed.
Yes if it is stuck open.
It's usually a vacuum leak.
Adjust your idle.
Please elaborate your question.
the engine runs at a faster rate than when the idle speed is lower.
First you must check the ISC motor ( idle speed control) operation. Its located by the throttle body. It controls idle and high idle speeds. Good luck
Car rentals cost so much because they are always nearly new cars and the rental company has to pay fees and high insurance premiums.
Your car will idle high until the engine begins to warm. You could set the idle to be a bit lower, but that may cause the engine to stall out when it's cold out. The engine should begin to lower the RPMs when it is warmed up.
How much does a new car cost?