Throttle body injection is an electronic fuel delivery system that replaces a traditional carburetor with one or two injectors mounted inside a central housing. The injectors spray atomized fuel into the air stream just above the throttle plates. The resulting air-fuel mixture then travels through a wet intake manifold to reach the individual cylinders. It offered better reliability and emissions control than carburetors but suffered from uneven fuel distribution compared to later multi-port designs.
We need to rebuild the TBI unit on that Chevy truck because the injector pods are leaking raw fuel onto the butterfly valves.
Mechanics often treat a TBI setup like an electronic carburetor during diagnostics, as both systems mix fuel and air centrally before routing it through a wet intake manifold.
Also heard as
- throttle body injection
- central fuel injection
- CFI
Do not mix it up with
- PFI: TBI sprays fuel centrally into the throttle body to feed all cylinders, whereas PFI places individual injectors right at each cylinder's intake port.
Related terms
EFI
Electronic Fuel Injection is a computer-controlled system that atomizes fuel into the engine.
Throttle body
A housing containing a pivoting valve that controls the amount of air entering a fuel-injected engine.
Intake manifold
The engine component that distributes incoming air or air-fuel mixture evenly to each cylinder.
PFI
This fuel delivery design positions the injectors just upstream of the intake valves.