Het H-T i have a b18c Type R in my ej8. Last night after i gased up and drove for a while my idle started to drop around 300-400 rpm and every once and a while it would bounce up and down between 1000 and 2500 rpm.

I stopped the car and let it sit for while started it up and it worked fine and idled like a dream, drove for a couple miles and got to a stop light and back at low idle.

This morning I cleaned the iacv and looked for some vaccum leaks. Nothing was found. idle is somewhat better now but after letter the car heat up and taking a small ride the idle was jumping up erraticly like before every time I would be in neutral or clutch.

I changed the plugs, wires, car, rotor last year when I put in the motor. Also it sounds like i'm giving little backfires from unburnt fuel.

What can be the problem?

TPS? Air in coolant lines? o2 sensor? Bad IACV?

Thanks in advance!