Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Fuel Injection System - Dual Unit TBI: Description
The General Motors dual unit (cross-fire) Electronic Fuel Injection (EFI) system consists of 9 major sub-assemblies: fuel supply system, Throttle Body Injector (TBI) assembly, Idle Air Control (IAC) system, Electronic Control Module (ECM), Electronic Spark Timing (EST), Electronic Spark Control (ESC), Hood Louver Control (HLC), data sensors and emission controls.
Fuel is supplied to engine through electronically pulsed (timed) injector valves located in separate throttle bodies on top of intake manifold (1 for each bank). Each throttle body unit is a Model 400 unit. The ECM controls amount of fuel metered through injector valves based upon engine demand and efficiency information. The ECM is a digital electronic computer which receives and computes signals from various data sensors.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.