I have a 1985 oldsmobil 98. I was driving down the road and it was back firing, and wouldn't go hardly at all. The car voice told me to stop the car because it said the engine pressure is low. I checked the oil and it was fine. The car will not start now. I looked at the battery and notice the red wire was lose so we tightened it and still did not start. Do you have any idea what the problem is? i don't