For Mazda Miata 1.8L 1839CC l4 GAS DOHC Naturally Aspirated 1999-2005. For Mazda MX-5 Miata 2.0L 2000CC 122Cu. l4 GAS DOHC Naturally Aspirated 2006. >> The idle valve ensures quicker ignition and more stable rpm at start-up, reduces starting hesitation and prevents "stalls" in icy or cold conditions.