Air Intake & Fuel Delivery

The air cleaner housing holds the engine air filter and mounts to the intake ducting. When the housing is cracked or broken, unfiltered air bypasses the element. The housing is vehicle-specific but typically straightforward to replace. Not included: the filter element itself — always install a fresh filter when replacing the housing.

The MAF sensor measures incoming air volume so the ECM can calculate the correct fuel dose. Symptoms of a failing MAF include rough idle, poor fuel economy, and hesitation under load. MAFs are often cleaned rather than replaced — use dedicated MAF cleaner spray before condemning the sensor. If buying used, ensure it's the correct part number for your engine variant (the same vehicle may have different MAF calibrations across engine options).

The throttle body meters airflow based on accelerator input. Common failure modes include carbon buildup (causing erratic idle) and a failed throttle position sensor (TPS). Many throttle bodies can be cleaned rather than replaced. If buying used, confirm the throttle plate moves freely and the TPS connector is intact. Some modern drive-by-wire throttle bodies require a relearn procedure after installation.

The intake manifold distributes air (or air-fuel mixture on carbureted engines) evenly to each cylinder. Plastic manifolds crack at EGR ports or coolant crossovers; aluminum manifolds warp at the gasket surface. When replacing, always use new gaskets. Not included: gaskets, EGR valve, fuel injectors, throttle body, or vacuum fittings — plan to transfer or replace these.

Fuel injectors atomize fuel directly into the intake port or cylinder. When buying used injectors, request flow test data or have them professionally tested and cleaned before installation. Match the injector impedance (high or low) and flow rate to your application. Related fuel injector parts include fuel rails, injector seals and O-rings, and clips — always replace seals when reinstalling injectors. Individual injectors are sometimes swapped; a full set ensures balanced fuel delivery.

On pre-fuel-injection vehicles, the carburetor handles both air metering and fuel delivery. Used carburetors are a viable option but should be rebuilt with a carburetor kit before installation — internal rubber components (needle valves, power valve, accelerator pump) degrade with age and ethanol exposure. Confirm the carburetor matches your engine's CFM requirement and mounting flange bolt pattern.