I have a question about my 1996 850 GLT. It seems that once the gas tank gets to about half empty, it starts driving occasionally in a jerky motion, as though a gas line is clogged up or the like. The check engine light goes on following this jerkiness. The way I have managed to solve this problem is to fill up the gas tank and make sure the gas cap is on tightly. In a few days, the check engine light goes away or turns off. So, now I refill my car when it is half empty to avoid this jerking motion that sets off the check engine light. I have come to the conclusion that the problem may involve any one of the following: faulty gas cap sensor, clogged gas filter, clogged gas line, etc.. Any clues or opinions from others would be appreciated in helping me diagnosis this problem before I spend lots of money. Many thanks.