A clogged fuel filter impedes the flow of fuel to the fuel injectors in the vehicle's engine. Fuel Pump U explains that since particle accumulation in the filter happens over time, some symptoms are not immediately noticeable.
According to Fuel Pump U, poor acceleration, power loss, misfires and engine cut-out are all signs of a clogged fuel filter. Even badly clogged fuel filters are capable of supplying the minimum amounts of fuel needed to power an engine under low-load conditions, so it is nearly impossible to diagnose a clogged fuel filter at idle or low speeds. AGCO Automotive Corporation recommends looking for these signs during situations like driving up a hill or while accelerating heavily.