I have a 1989 Dodge Aries K 4 cylinder 2.5 liter engine with an automatic transmission. When I start the car from a cold position, it idles smoothly. But after approximately 8-10 minutes, the car begins to idle roughly and then black smoke comes out from the muffler instead of the normal gray smoke.

Hoping to address the root cause of the problem, I have installed the following parts: a new throttle body, a new EGR valve, a new distributor shaft and cap, a MAP sensor, a new coolant sensor, new spark plug wires, four new spark plugs, a new ignition coil and a new air cleaner filter.

What am I missing???