I have a 1992 Civic, I believe a DX model. 4 cylinder, auto that idles fine when first started but once warm will cycle between around 2000 rpm and normal idle when ever stopped, this cause the car to surge if the brake isn't pressed fairly hard. Will rev up and down in drive, park, or neutral. The check engine light is on so I assume a bad sensor is to fault, or maybe a vacuum leak. Any ideas or suggestions?

. Check for codes:

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-hondas-selected-other-vehicles-46563-6.html#post832012

. Clean the throttle, throttle body, upper & lower ports, and Idle Air Control Valve (IACV):

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-hondas-selected-other-vehicles-46563-7.html#post1054149

. Read the link below:

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-hondas-selected-other-vehicles-46563-3.html#post260436

. Replace the Ignition Control Module and coil:

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-hondas-selected-other-vehicles-46563-4.html#post265896