Ch. 86 Catalytic Converters
For most effective catalytic converter operation, the air-fuel mixture should be near________.
14.7:1
A catalytic converter has to be at least how hot before it starts to work?
500°F (260°C)
Which of the following is true of catalytic converters?
A lean exhaust is required to oxidize hydrocarbons (HC) and carbon monoxide (CO).
When checking catalytic converter temperatures, the inlet temperature should be________ when compared to the outlet.
About 10% cooler
When testing the exhaust system with a pressure gauge, where is the gaugeattached?
At the pre-catalyst O2 sensor hole
Technician A says that the catalytic converter is warranted for eight years or 80,000 mi, whichever comes first. Technician B says that after replacing the catalytic converter, the old converter must be kept for possible inspection for 60 days. Which technician is correct?
Both Technicians A and B
Two technicians are discussing testing a catalytic converter. Technician A says that a vacuum gauge can be used and observed to see if the vacuum drops with the engine at 2500 RPM for 30 seconds. Technician B says that a pressure gauge can be used to check for back pressure. Which technician is correct?
Both Technicians A and B
Technicians were discussing the construction of a catalytic converter. Technician A stated that the ceramic substrate in monolithic converters is not restrictive. Technician B stated that monolithic converters can be serviced only as a unit. Which of the following statements about this scenario is true?
Both technician A's and B's assessments are accurate.
Technicians were discussing the factors that could damage a catalytic converter. Technician A stated that engine misfire can damage the catalytic converter. Technician B stated that intake manifold leaks can damage the catalytic converter. Which of the following statements about this scenario is true?
Both technician A's and B's assessments are accurate.
A catalytic converter rattles when tapped on with a mallet. What does this indicate?
Broken substrate inside the converter
Which exhaust gas reading indicates a good catalytic converter?
CO is zero
________ is an element that is used to store and provide oxygen to the oxidation bed of the converter when the exhaust is rich and lacks enough oxygen for proper oxidation.
Cerium
A clogged exhaust system will cause the vacuum reading to ________ as the engine RPM is increased to 2500.
Drop
A P0422 (catalytic converter efficiency failure) is set. What is a possible cause?
Engine mechanical fault, Exhaust leak, and Fuel contamination
A catalytic converter can be harmed by ____.
Excessive engine oil, antifreeze, and sulfur from poor-quality fuel
Which of the following can initiate the P0422 diagnostic trouble code (DTC)?
Fuel contaminants
Which of the following is true of catalytic converter diagnosis?
If the vacuum pressure of an engine at 2,500 RPM is equal to the vacuum reading when the engine is at idle, the exhaust system is not restricted.
Technicians were arguing about the working of a catalytic converter. Technician A stated that a catalytic converter can operate when it is cold. Technician B stated that a catalytic converter must be heated close to 500°F before it starts working. Which of the following statements about this scenario is true?
Only technician B's assessment is accurate.
Technicians were discussing the snap-throttle test. Technician A stated that a converter is not working properly if the oxygen reading at wide-open throttle (WOT) in park is less than 1.2%. Technician B stated that a converter may have low efficiency if the oxygen reading rises to about 1.2%. Which of the following statements about this scenario is true?
Only technician B's assessment is accurate.
Which diagnostic trouble code (DTC) is initiated by exhaust leaks?
P0422
What two primary sensors does the PCM use to check the catalytic converter?
Precat and postcat oxygen sensor
Two technicians are discussing catalytic converters. Technician A says that the exhaust mixture must be at stoictiometric for the best efficiency. Technician B says that the air-fuel mixture must be leaner than 14.7:1 for best performance from a three-way catalytic converter. Which technician is correct?
Technician A only
A catalytic converter is being tested with an infrared pyrometer. Which is an acceptable (good converter) result?
The outlet should be hotter than the inlet by 10%.
A catalytic converter converts harmful exhaust gases into ________.
water vapor and carbon dioxide
If the oxygen reading of an exhaust gas analyzer exceeds a value of ________, the converter is not working.
1.2%
The temperature of a catalytic converter should increase by at least ________ if it is working properly.
10%
A(n) ________ is a chemical that helps start a chemical reaction but does not enter into the chemical reaction.
catalyst
A(n) ________ is an after-treatment device used to reduce exhaust emission outside the engine.
catalytic converter
For efficient operation, a catalytic converter must be located ________.
closer to the exhaust manifold
With on-board diagnosis (OBD)-II-equipped vehicles, catalytic converter performance is monitored by a(n) ________.
heated oxygen (HO2S) sensor
Pressure in the exhaust system at idle should be ________.
less than 1.5 PSI
The maximum back pressure of the exhaust system should be ________.
less than 2.5 PSI at 2,500 RPM
A catalytic converter can be destroyed by excessive temperatures caused by ________.
long idling period
What is applied to the ceramic substrate to make the surface porous?
Washcoat
A catalytic converter is not functioning correctly if ________.
carbon monoxide in the exhaust in greater than zero
