Idles high in park and drives at 40 mph wth out me putting gas

Sounds like a bad spark plug, spark plug wire. Probably the spark plug wire. They usually act that way when load is applied. It may misfire under light load and not at idle. Try plugs and wires.

Possibly but to find the fault have the fault codes read . It may be the accelerator position sensor . Don't waste money until you have the codes to point you in the right direction

Back to the mechanic - sounds like either an IAC motor or TPS sensor is the problem, but also could be the throttle cable (sticking leaving the throttle not fully closed).

Did you check the airflow sensor? Clean it, maybe it will help

Sounds like the Throttle Position sensor or the Idle Air Control Valve causing the issue

that is a possibility. is this a guarantee to fix? if he has done the proper diagnostics and he is guarantee the repair then this would be logical. but no fix no pay. dont let it turn into something else and something else. hope this helps

replace the idle air control valve {sensor}

Throtle position motor faulty

Look for a vacuum leak somewhere. This is the most common problem for a high idle.

I have a 2001 Nissan Altima and mine did the same thing. We replaced the intake gasket. It costs around $5.50, but it requires several different kinds of tools. We spent over $100 in special sockets, etc. But once you replace that gasket, it will idle better.