问：发动机曲柄，点火速度很慢，汽车不会启动

For the past 4 weeks (and becoming more and more frequent), when I first try to start my car in the mornings or after work at the end of the day (any time the car has been sitting for hours), the engine won’t start. This is a random problem and doesn’t happen all the time. This is what happens: Everything seems normal and the engine cranks but doesn’t fire up. The ignition sound it makes seems normal, except that it sounds much slower than usual and takes twice as long. Then, it suddenly stops. Once when it happened at night, the lights went dim. There are no warning lights. I cleaned the battery terminals for corrosion and I also cleaned the distribution caps. What is your advice to fix these problems?