i have a 96 volvo 850. It has been working for a charm, until I ran out of gas. After I ran out, I put more in, and the "Check engine" light was on. Then it went off after a day. The next day, I made a 2 hr drive. Then, my car sat for a day or two, and the light was back on. It was also very low on gas at this point, but not out. I noticed that there was blackish grayish smoke coming out, but my friend said that's because you are burning the stuff that settled at the bottom of your gas tank (not sure if this is true.) So, we put in more gas, and it was smokey for about a minute then it was clean again. But the light continued to be on. Then, this happened twice, both times I was on a hill: The gauge will go from 1/6th tank of gas to empty, and my car will sound like its out of gas and cut off. After a restart, it'll work fine again. But right before it cuts off, it is smokey. Can someone guide me? thanks!!!