Ford Tempo/Topaz 1984-1994 Repair Guide

Gasoline Engines


The converter contains 2 separate ceramic honeycombs coated with different catalytic material. The front catalyst is coated with a rhodium/platinum catalyst designed to control Oxides of Nitrogen (NOx), unburned Hydrocarbons (HC) and Carbon Monoxide (CO). This is therefore called a Three way Catalytic Converter (TWC). The rear catalyst is coated with platinum/palladium and is called a Conventional Oxidation Catalyst (COC).

The TWC converter operates on the exhaust gases as they arrive from the engine. As the gases flow from the TWC to the COC converter, they mix with the air in the secondary air system into the mixing chamber between the two ceramic honeycombs. This air is required for optimum operating conditions for the oxidation of the HC and CO on the COC converter. Air is diverted upstream of the TWC during cold start to provide faster catalyst light off and better HC/CO control.

The factory installed exhaust system uses a one-piece converter system. The exhaust system is usually serviced in 4 pieces. The rear section of the muffler inlet pipe (intermediate muffler inlet) is furnished separate from the muffler.

The operating temperature of the exhaust system is very high. Never attempt to service any part of the system until it has cooled. Be especially careful when working around the catalytic converter. The temperature of the converter rise to high level after only a few minutes of operating temperature.