Car idles at 500 rpm now does not start

This is called hunting. Can be caused by a bad mass air flow sensor. Could also be a sticking idle air control valve.

Check the fuel pressure regulator diaphragm.
Do It Yourself Diagnosis and Repair

First ensure that the throttle interior is really clean, a surface layer of grime can upset the ECU's ability to meter and govern the air entering the engine. If the throttle body interior is found to be really oily and dirty check on the idle air control valve and make sure that it too is cleaned up. Next put the ignition switch in position 2 (on, but no start) and depress the accelerator fully and release. If there is an issue with the throttle position sensor this procedure can help the ECU relocate the throttle plate position. Start the engine and if it is still hunting locate the air mass meter (AMM) on the air ducting immediately next to the air filter and disconnect the electrical connection. Does this remove the hunting aspect?... the rev speed might change but for the moment concentrate on the evenness of the tick-over. If the idle is even when the AMM is disconnected but hunts when connected then look at replacing your AMM. Try spraying the AMM with no residue electrical cleaning spray to see if this improves matters.

My vg30 dnt rev more than. 2200

Hi.it sound a lot like a ignition coil coils tend to do that if its got a crack it Swell when the temperature rises

Try to disconnect the Air Flow Meter. It is the first plug just before the air filter/air intake box. If this improves your situation you will need to source a new or aftermarket Air Flow Meter.

got same prob help us !!!

hi there have you check the air flow system (pipes for blockages,pipes that may have split etc) sounds if it is air flow problem.

Change all the filters (fuel and air). check and see if all your spark plugs are firing or just change them. if it is fuel injected make sure your injectors are working. Hope something there helps get it running good.

rx7`s should rev to 3000 when started cold then it should settle to 750 to 1000 after about 30 to 60 seconds.
mine suffers a similar problem. so far I have been told various answers, mostly involving the bac valve, lambda sensor, air flow meter, etc. try starting of by adjusting the idle adjust screw (on top of the throttle body under plastic cover) this may be all it is. I have not had time to do mine. Its been fine otherwise and idles fine after a few minutes. mine is non turbo 87.