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

Have you tried cleaning the throttle body? When did you last change the spark plugs?

Back in the old pre injection days the heat crossover in the intake manifold would get clogged with black crap. It would run bad cold. We would have to pull the manifold and dig out the junk with a coathanger. I dont know if that was still a problem in later models.

Before I did anything I'd get the computer codes.

Cycle the key on-off-on-off-on (without starting engine) then count the light flashes. the codes will be 2 digits. Usually you will see a 12 (one flash, a pause, then two flashes) and a 55 (five flashes, then a pause and five more flashes. there will be a longer pause between codes).

Tell us what you got.

Stock thermostat? Check the heat to manifold and make sure coil is not going bad

Yes stock thermostat. I got the codes this morning they were 12 37 33 86 and 55. thanks for help and suggestions so far.

There is no 86 code might want to check it again.

http://www.straighttalkautomotive.com/OBD1/chrysler-OBD-I.html

sorry the 86 is actually a 17 and a 15 so codes are 12 37 33 17 15 and 55. from what I saw some make sense. Truck always has run cold barely moving heat gauge up since I've owned it(about 8 years)so code 17 makes sense and since it was fine for so many years I don't see this is the issue. Code 37 is interesting because I have a clunk from time to time I suspected was torque converter related. When I got it inspected they said it was internal issue but as my fluid is not burnt and extremely clean and shifts perfectly I had ignored it.
This still does not explain the wandering idle in cooler temps. 33 has me perplexed as this is non ac truck. No idea what code 15 could mean as I have no idea what a distance sensor is (VSS).

also this is a 3 speed auto no od

33 is normal in a no AC vehicle.

No VSS is probably most of your problem, and too cold a thermostat is the rest of it. VSS tell the computer if the truck is moving and how fast. Without it the computer has no idea and you start to see stumbles and stalls, especially when stopped.

with 37 there I almost think it's a wiring issue and both VSS and TC codes are present. I seem to have a vague recollection about wires getting corroded back behind the battery causing issues.

VSS screws into the trans at the speedometer cable connection
https://tinyurl.com/y7omwhne

Went though this last winter,ran fine till the temps got down in the 30s on a 89. Changed the injectors and ran perfect