Hi i have a 1992 honda civic si 3dr with a d16z6 sohc vtec and i cant seem to find out why it idles so high. When it is started cold in the morning it will idle at 2500 rpms after about 5-10 minutes it will start to idle down to 1500 then continue to decrease to 500 rpms. After it has warmed up it will stay steady at around 1000 rpms but it tends to surge up and down for 1000 rpms this is really getting anoying and I am not sure why it is doing this if you have any thoughs on it let me know?

 

Sound like ur thermo fast idle valve in ur throttle body may be clogged or not working take ur intake off and there should be 2 small holes inside the throttle body start ur car when it's warmed up and put ur finger over each hole im thinking the bottom one is the thermal fast idle one if it stops that's ur problem

 

Thanks I will give that a try

 

ok i tried covering the wholes in the throttle body and that made it idle fine when it wasnt warmed up but when the top hole was covered it made a very big diference while it iddled cold. When it warmed up i covered one of the wholes and nothing happened so i tried the other and still nothing happened. Got any other suggestions?