what part is causing car to be unable to idle without me keeping my foot on gas till it’s warmed up in morning? It does not act like that at lunchtime & 5pm no matter what the temp gauge reads when I get in it at lunchtime & 5pm: at those times, it just cranks and stays on till I shut it off.
You don’t say what model 85 Volvo you have, but a common component with all the engines of this year is the cold start injector. The cold start injector adds just a small amount of extra fuel to the engine when the engine is started cold. The engine computer determines when the cold start injector should function by a signal it recieves from the coolant temperature sensor for the computer. Don’t confuse this with what the coolant temperature on the gauge indicates. As there’s a seperate sensor for the gauge on the dash and a seperate sensor for the computer.
So it could be that the coolant temperature sensor for the computer is faulty where it’s telling the computer the engine is at operating temperature when it’s not when the engine is started cold, or the cold start injector isn’t functioning.