Many of the tests a buyer should run on a four-cylinder car before purchasing are the same as on cars with other engine configurations, such as looking for leaks, poor performance or damaged interiors. The buyer should also run an engine compression test to check each individual cylinder.
An engine compression test is a special type of examination that uses a tool called a compression gauge to find out how efficient the engine's cylinders are functioning. A consumer is able to run the test himself by placing the car in park, disconnecting the distributor and fuel injection system and removing each spark plug. The gauge is connected to the car's battery and inserted into the hole left by the spark plug to test the power of each cylinder when the car is turned on.
Other tests involve similar inspections of the engine and its internal parts. The buyer should also test drive the car after inspecting the engine, paying close attention to the way the car shifts gears, accelerates, decelerates and breaks. Driving the car under normal and slightly intense conditions gives the buyer a good idea of how it handles and the general state of the vehicle. The buyer should also look at the interior for stains in the fabric or issues with the dashboard.