1989 d150 with 318 and factory throttle body injection (headache) automatic runs great when temperature is 70 plus. It runs like crap when it gets colder. Been a hot summer here and truck has been running good. I started having issues past winter with a surging idle. Races up to about 1500 rpm then drops down to 500 and almost stalls(sometimes it does stall). Will hesitate even when cruising at 55 mph plus acting almost like a miss. Bucks when at low speeds. Sometimes it smooths out after engine warms up most times it doesn't. Outside air temp seems to be culprit that brings on this condition.

I had almost forgotten about this as it got hot here and truck has been running like a champ smooth idle no misses etc... Today cold front came in and temps dropped into 60s and it started running like crap again. Idle racing etc... It did smooth out after about 15 minutes though. What the heck is going on? I am assuming it is something to do with idle speed control or choke related that kicks on when it gets a little colder out. Truck is all stock about 70k miles on it. No service engine soon light on. Any Help/Ideas would be appreciated. TIA