I can drive my car around 20 miles and smoke will come out from under the hood,

smoke or steam?is it running hot?oil leaking on exaust?

I've had almost the exact same thing happen in my 1989 Cressida. Black smoke pours out from under the hood after driving about 20 miles and I can't see through the windshield it's so thick. Do you have any answers as to what went wrong in a perfectly driving car before then? I've had someone tell me that the sensors must be broken and the right fuel mixture isn't being delivered.