Hi there , i have just bought a 1999 Nissan skyline R32 GTE, at idle the revs hunt from300 to 900, nd it has a constant eratic miss fire at idle,, when you on the road and accelerating , it has a flat spot , but never in the same spot ???? what could be causing the problem ??? i cleaned the AAc valve and it sorted the problem for a short while ???? but its back now ???