Automotive terms explained
The exhaust gas recirculation (EGR) valve is an emissions component that routes a small amount of exhaust back into the intake manifold to lower combustion temperature and reduce nitrogen oxide (NOx) formation. When it fails, you’ll typically see a check engine light, rough idle, or failed emissions test—often with diagnostic code P0401 (insufficient flow) or…
A vacuum leak is an unintended opening in your engine’s intake system that lets unmetered air rush in after the mass air flow (MAF) sensor. That extra air throws off the air-fuel ratio, making the engine run lean. The most common cause is a cracked, brittle, or disconnected vacuum hose. Typical symptoms include a rough…
An engine compression test measures the pressure each cylinder builds during the compression stroke. That number tells you how well the piston rings, valves, and head gasket are sealing. If compression is low in one or more cylinders, your engine is losing power, misfiring, or burning oil. You can run this test yourself with a…
Engine knocking—also called detonation or pinging—is a metallic rattling noise caused by fuel igniting at the wrong time inside the cylinder. Instead of a smooth, controlled burn, the fuel explodes in uneven pockets, sending shock waves that hammer the pistons, rings, and bearings. The most common trigger is using fuel with too low an octane…
Both a supercharger and a turbocharger force extra air into your engine to make more power, but they differ in where they get the energy to do it. A supercharger is belt-driven off the crankshaft, so it builds boost instantly from idle. A turbocharger is exhaust-driven, which creates a delay (turbo lag) but doesn’t steal…
A turbocharger uses exhaust gas to spin a turbine that forces extra air into the engine, letting it burn more fuel and make more power without increasing engine size. A 2.0-liter four-cylinder with a turbo can produce 250–300 hp instead of 150 hp, while still getting decent highway fuel economy when you stay out of…
Direct injection sprays fuel straight into the combustion chamber under high pressure. Port injection sprays fuel into the intake runner just ahead of the intake valve. Direct injection delivers better fuel economy and power, but it causes carbon buildup on intake valves because no fuel washes over them. Port injection is an older design that…