These devices are used to oxidize excess carbon monoxide (CO) and hydrocarbons (HC) in the exhaust gases before they can escape out the tailpipe and into the atmosphere. The converter is installed in front of the mufflers, underneath the car and is protected by a heat shield. Many 1977 and later models are equipped with "miniox" converters as well as the main underfloor one.
The expected catalyst life is 50,000 miles, provided that the engine is kept in tune and unleaded fuel is used.
To keep the catalyst from being overheated by an overly rich mixture during deceleration, a catalyst protection system (CPS) is used on some models. The system consists of a throttle positioner solenoid (not to be confused with the idle stop solenoid), a control box, and an engine rpm sensor.
Any time that the engine speed is more than 2,000 rpm while decelerating from highway speeds, the solenoid is energized and keeps the throttle butterfly from fully closing, thus preventing the mixture from becoming too rich.
REMOVAL & INSTALLATION
The converter used is the monolithic (one-piece) type which cannot be refilled.
If the catalyst fails, it will be necessary to replace the entire converter assembly. To do so:
- If a grass shield is used, remove the bolts which secure it and lower the shield from underneath the vehicle.
- Unbolt the converter assembly at the mounting flanges, just as you would a normal exhaust pipe from the manifold.
Support the exhaust pipe while the converter is removed.
- Replace the old converter with the new unit.
- Remove the plastic plugs from the ends of the new converter (if used) and install it in the reverse order of removal, being sure to use all required gaskets to ensure a leak-free fit.
- Install the grass shields.