Cold natured diesel???

[vaman4215]

Just picked up this 84 300D this past week. Had to do some minor stuff to it, put in a windshield, etc....It's been cool down here in Va last couple of days, today temps only got up to 55 or 60....I noticed a few days ago, when you crank this one up, it runs real rough upon startup and only will stay running if you hold down the gas, like the idle speed is set way too low..She won't even stay running unless you hold the throttle open a tad...After about 3-5 minutes of holding throttle open, she will idle like normal around 500 rpm...It didn't do this when I first got the car as it was warmer then.....Any ideas????