📖 What It Does
Atomizes fuel inside the cylinder at very high pressure (500–3,000 psi). The cooling effect of fuel evaporating inside the cylinder also lets engines run higher compression for more power.
⚙ How It Works
A high-pressure mechanical fuel pump driven off the camshaft pressurizes fuel to thousands of psi. Solenoid-controlled injectors fire multiple precise pulses per combustion event directly into the chamber. The ECU tunes timing and quantity based on load and RPM.
⚠ Symptoms When It Fails
Hard cold starts, misfires, rough idle, P0300-series codes, and a slowly creeping power loss are typical. The intake valves are not washed by fuel any more, so oil vapors and EGR carbon stick to them - leading to "carbon buildup" that often needs a walnut blast to fix. See full symptom guide.
💰 Replacement Cost
Injector replacement: $400–$1,200. GDI injectors are 5–10× more expensive than port injectors. Walnut-blasting the intake valves runs $500–$900. See injector cost.
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❓ Frequently Asked Questions
How do I prevent carbon buildup on GDI?
Use top-tier gas, regular oil changes with low-SAPS oil, and consider a catch can. Some people walnut blast every 60,000 miles.
Is direct injection better than port injection?
For power and economy yes. For long-term cleanliness, port injection wins. Many modern engines use both.
Why are GDI cars so loud at idle?
High-pressure injectors clatter audibly. It is normal.
Does premium fuel help GDI engines?
Only if the engine requires it. Top-tier detergents matter more than octane for cleanliness.
What is a fuel catch can?
An oil separator on the PCV system that traps vapors before they coat the intake valves.
Are GDI engines reliable?
Generally yes, but expect higher service costs at 80,000–100,000 miles for valve cleaning and injectors.