The 2001-2005 Civic EX was equipped with a 1.7L engine that produced up to 127 horsepower and 114 lb-ft of torque. The engine was known for its reliability and efficiency, making it a popular choice for those seeking an affordable and practical car. The engine had potential for upgrades, with aftermarket parts readily available to increase horsepower and performance. Some popular modifications included adding a cold air intake, installing a performance exhaust system, and upgrading the engine's computer chip. With these modifications, the engine could produce up to 150-160 horsepower, significantly improving the car's performance. Overall, the 1.7L engine in the 2001-2005 Civic EX offered a good balance of reliability, efficiency, and potential for upgrades.