Toxic gases emitted by internal automotive combustion are responsible for air pollution and deterioration of human health. Therefore, in this study modified zeolite was evaluated as an alternative catalyst for reducing automotive gases in a catalytic converter. For the study, the CuZSM-5 zeolite was synthesized by the hydrothermal method, exchanged with copper ions and then installed in the exhaust of a T3 Bi-Fuel engine. The experiments were carried out on an auto model 1984 Toyota, with and without a catalytic converter at different revolutions per minute (rpm) as idle, average and maximum, using the HGA 400 4GR gas analyser to measure hydrocarbon (HC) and carbon monoxide (CO). The results showed a significant reduction in LPG engine of Hydrocarbon Propane (78 %) and CO (60 %) at high rpm; while in gasoline engine was reduced at Hexane (29 %) and carbon monoxide (68 %) at low rpm. This showed that Cu-zeolite is efficient in reducing gases and more economical than the commercial converter.