Santana PS10 with a mind of it's own?

Iveco engine in my Santana ps10 ststion wagon start first time every time and will drive perfect most of the time then the rev will just cut to idle speed with nothing on the accel pedal for 2-5 seconds then it's back to normal as if nothing happen. With the cold weather at present it just don't want to move ,and will start as normal but will not go above 15 hundred revs with the engine sound like very weak mixrure and the EDC test flashing. Take your foot off the accel pedal and in a few seconds EDC light goes off and idle speed back to normal and will only rev up to 1500-2000 revs then cut back to idle with EDC flafhing and weak mixture sound. HELP . Thanks (Roy)