Scan for Trouble Codes
Check to see if the "service engine soon" light is on, if not continue to the next step. If the "check engine" light is illuminated you need to have the computer scanned for trouble codes. Use a simple scanner tool to retrieve trouble codes and check if they relate to the specific problem.
Check the Air Filter
A plugged air filter will not allowing the proper amount of air into the engine. If air is not allowed to enter the engine's intake it will limit the engine power output. To check your engine air filter open the hood and remove the air filter from its housing and inspect, replace as needed and recheck.
Check the Fuel Filter
Several conditions can cause low power, one of the most common reasons is a clogged fuel filter not allowing the proper amount of fuel pressure and volume into the fuel injection system. To check for this condition remove the fuel filter and drain excess fuel from the filter, next wipe any excess fuel from the filter. By blowing through the filter you can determine if the filter is clogged, you should be able to blow through it very easily. If you cannot blow through it or it is difficult replace the fuel filter with a new unit and the recheck system.
Check Fuel Pump Pressure and Pressure Regulator
Fuel pump is worn providing low fuel pressure to the fuel injection system. A fuel pump that is faltering providing low system fuel pressure/volume will cause low power. Your car's engine depends on constant fuel under pressure to supply the fuel injection system properly. Your car's fuel pump performs this action and is located in or near the gas tank. The injection system meters fuel through the injectors and into the engine. Many engine run drivability problems can be related to a weak or failing fuel pump. Problems can range from hard starting in the morning, low power and stalling while driving. Most vehicles have a fuel pressure test port somewhere on the fuel rail, use a flashlight to locate it on your engine or consult a repair manual.
Checking the MAF
(mass air flow) and MAP (manifold absolute pressure) sensors. The MAF or MAP help the ECM/PCM determine how much air the engine is consuming and distributes the proper amount of fuel. If these sensors become weak they can misread and cause the ECM/PCM to think the engine is turning slower than it is, in turn giving the engine less fuel and producing less power.
Check for severely worn or misadjusted spark plugs
Engine timing is crucial to power output, if the spark plugs are severely worn or have a misadjusted air gap the timing of the spark can be delayed or ineffective causing power loss. To check your engine's spark plugs wait until the engine is cold, then remove any spark plug and inspect.
Check the timing belt or timing chain setting
The crankshaft and camshaft must stay in proper correlation. The procedure for checking crankshaft to camshaft correlation varies on each car. You will need to gain access to the timing belt or chain marks. Once you have gained access check your timing marks here, timing belt or timing chain setting.
Check the exhaust system for blockage
A plugged catalytic converter can cause low engine power by not allowing the engine exhaust to exit the engine properly.
Check the engine compression
As the engine depends on compression to ignite the fuel air mixture. If an engine has major wear is will not produce the proper amount of power. A compression test can be performed to check for wear or internal damage. A compression gauge is needed to test the engine cylinders.