Which emission controls are required on a Federally certified 1976 Jeep with a 4.2L engine?

• A. CAT, OXY, AIS, EGR, TAC, PCV.
• B. PCV, TAC, EGR, AIS, OXY, CAT.
• C. PCV, EGR, and TAC only.
• D. PCV, TAC, EGR, AIS, OXY, CAT, and DPF.

Answer: (B)

Federal emission controls in 1976 were implemented as a complete package to reduce HC, CO, and NOx, and a federally certified 4.2L Jeep from that era would require six specific components working together. The PCV system recycles crankcase vapors back into the intake to burn them instead of releasing them, cutting hydrocarbon emissions. The TAC Valve, or thermal air control, times the air-injection system so it operates properly once the engine reaches operating temperature, helping the exhaust receive extra air when appropriate without causing cold-start issues. The EGR valve feeds a portion of exhaust back into the intake to lower combustion temperatures, which reduces NOx formation. The AIS, or air injection system, pumps fresh air into the exhaust to promote oxidation of remaining HC and CO. The oxygen sensor (OXY) provides feedback to maintain the proper air–fuel mixture, enabling efficient combustion and lower emissions in closed-loop operation. The catalytic converter (CAT) then chemically converts HC, CO, and NOx into less harmful substances. The diesel-era device like a diesel particulate filter (DPF) does not apply to a 1976 gasoline engine, so it isn’t part of the required setup.