The idle control switch allows the generator to go into idle when there is no demand form the appliances connected. This saves gas and increases the life of the generator. Damage can occur for some appliances like a refrigerator/freezer because the voltage and frequency are not prepared for the load resulting in a low voltage bad startup that will damage the appliance. Suggest that you leave the idle control switch off while any motor/electronic devices are connected.
The throttle control is likely a choke function for starting. These generators are designed for only one running speed to produce the necessary 60 cycles per second and voltage.
The following link is to a Canadian web site that later in the detail report describes the concern of idle control. In addition it provides good insight to the operation and use of portable generators
Hope this helps?
Understanding Portable Generators
The user manual see pages:
http://www.mikestools.com/download/Porter-Cable-Manuals/Porter-Cable-CTE300.pdf
you should be able to do it by ear,With a load on the unit you should be able to idle it to where it sounds like it is not running to fast and that it is not running enough to keep it from triping the reset.it should sound smooth. or idle it to around 2000 rpms or lower.
You need an multi meter, on the ohms scale. Short the two prongs on the cap out, removing any voltage on it. Put your meter to a mid range ohms scale. Touch the leads to the prongs on cap and watch your meter. It should start climbing in value and then go to 'OL' if it's digital. If it's an analog meter(with a needle) it will go all the way over to 'infinite. This means it's good. If it's bad, it will just read 'OL' or go right to 'zero' meaning it's either shorted or open. If you need further help, I’m available over the phone at https://www.6ya.com/expert/craig_3fa289bf857b1a3c