At the end of 1990, the fourth and final series was introduced: new interior fabrics, new bodywork colors, Dedra-style diamond-cut alloy wheels, total elimination of rear identification writings, elimination of the 1300 engine (the LX versions will only be with the 1500 engine), bonnet 8v Integrale style engine with white front indicators. The 1500 LX also receives the instrument cluster with the HF-style circular warning lights. The GT i.e. it is upgraded to 111 HP like the contemporary Prisma. The HF Turbo versions now featured the front with split round headlights and the rounded bonnet like the Integrale 16v.

When the Lancia Delta was born, no competition versions were envisaged, given that in the rally field the teams of the Fiat-Lancia Group raced with victorious cars such as the 131 Abarth and Stratos initially, and with the Lancia Rally 037 later. However, starting in 1982 an all-wheel drive prototype was presented at the Turin Motor Show. The mechanics and chassis were those of the basic model; the engine had a double overhead camshaft, 1600 cm³ with turbocharger; it delivered 166 HP. A transfer differential with longitudinal drive for transmission to the rear wheels was mounted on the gearbox-differential group. A self-locking differential was housed on the rear axle.