hi guys need help. car been parked over a year now its a 98 civic tried to start the vehicle started fine when it warmed the idle started jumping about 1000-2000rpm. took the map sensor off and put finger on hole the idle became stable thought was faulty. changed the sensor but still no joy. oh yea the plugs had a black soot on them aswell changed them also still same help please thanks in advance.

 

your IAC ( Idle air control valve) is either clogged or faulty. most likely its clogged from sitting. Taking the MAP sensor out will made it idle stable, but then your also running extremely rich, and will get terrible gas milage, not to mention you will shoot so much black smoke, especially when you hit VTEC.. ive had this prob before, you literally get a layer of black soot on the back bumper.

Solution: Take out your IAC, located on the back of your manifold, assuming its a Y8 motor (vtec) and clean out the gunk from the two openings. If that doenst help, then the unit itself needs to be replaced.

 

Do a search. I had the same issue with my car recentely, so I took out the IACV, cleaned it out, but still no go. I then took out my FITV, cleaned it out, and my car now purrs like a kitten at 800 rpms. The fact your saying that its doing it when the car is warmed up would lead me to believe that its just your IACV thats acting up.

Search: IACV, FITV.

 

If you plugged up the hole inside the left of the throttle body then its your fitv Take it off and tighten the wax like cap.