There are a few different reasons that could cause your engine to lose power. If you have a loss in power, it's important to first check your engine oil level and quality. If the oil is low or dirty, it could be causing your engine to run less efficiently. Another possibility is that your fuel filter is dirty and needs to be replaced. A clogged fuel filter can restrict the flow of fuel to the engine, causing a loss in power. Finally, if your spark plugs are fouled or worn out, they may not be firing correctly and could be causing a loss of power. If you're experiencing a loss of power, it's best to take your car to a mechanic so they can diagnose the problem and get your car running correctly again.