How to Add Horsepower to a Grand Marquisby Scott Eilers; Updated November 07, 2017
Ford designed and produced the Grand Marquis, a full-sized sedan sold under the Mercury badge, which was typically for luxury-trim levels of Ford vehicles. After producing the Grand Marquis from 1983 to 2010, Ford decided the Mercury brand was no longer financially viable and halted production of all Mercury vehicles. Although it's not a performance vehicle, there are a substantial number of aftermarket products available for it, many of which increase horsepower.
Replace the Grand Marquis engine control chip with a performance aftermarket control chip. The engine control chip, or engine control unit, is responsible for managing the electronic fuel injection (EFI) system. Factory engine control chips are fairly restrictive in order to maximize safety and fuel efficiency, especially in non-performance oriented vehicles such as the Grand Marquis. Performance oriented engine control chips will reprogram the functioning of the EFI system for maximum performance, which may decrease fuel economy but will substantially increase horsepower.
Replace the Grand Marquis air intake with a performance cold-air intake. The factory air intake on the Grand Marquis is fairly restrictive in order to keep engine noise and cabin noise minimal. A performance cold-air intake will allow more air to enter the combustible air/fuel mixture inside the engine, which provides more available horsepower.
Replace the Grand Marquis exhaust system with a performance exhaust system. As with the air intake, the Grand Marquis factory exhaust system restricts airflow in order to maintain a quiet cabin, as well as to minimize CO2 emissions. Although installing a performance exhaust system will increase engine noise and emissions, it will also increase available horsepower by allowing the Grand Marquis engine to release hot air and engine pressure more efficiently. Further, many Grand Marquis owners enjoy the louder, more aggressive sound that a performance exhaust system produces. Make sure to consult state regulations before performing this step, as some states prohibit aftermarket exhaust systems.