I'm almost 99% sure you have low compression. I had a '85 Accord that did the same thing to me on the way home from work. Was running fine, loud boom, and smoked really bad. I shut the car off and cruised as far as I could to a gas station. Got out looked over some basic stuff, checked for everything... Was a good 4 to 5 miles from my house and my phone was dead. I wasn't going to walk so I started her back up. Ran fine...like nothing ever happened... Almost home it did the same thing... I just did limb it in the driveway. Next day started up fine. I put her beside the garage and found out after I did a compression test #3 cylinder was shot.