positive crank and catalytic converter

What are the three most commonly used catalysts in a catalytic converter?

1) Rhodium 2) Palladium 3) Platinum

What tests can be performed by a service technician to test the catalytic converter?

1) Tap test- tapping on the catalytic converter using a rubber mallet. If the substrate inside the converter is broken, the converter will rattle when hit. If the converter rattles, a replacement converter is required 2) Back pressure test with a pressure gauge - installing a pressure gauge in an exhaust opening A. To test an oxygen sensor, remove the inside of an old, discarded oxygen sensor and thread in an adapter to convert it to a vacuum or pressure gauge. B. To test the exhaust back pressure at the exhaust gas recirculation (EGR) valve, remove the EGR valve and fabricate a plate equipped with a fitting for a pressure gauge. C. To test at the secondary air-injection (SAI) check valve, remove the check valve from the exhaust tubes leading to the exhaust manifold. Use a rubber cone with a tube inside to seal against the exhaust tube. Connect the tube to a pressure gauge 3) Back pressure test with a vacuum gauge - exhaust restriction can be tested indirectly by checking the intake manifold vacuum with the engine operating at a fast idle speed (about 2,500 RPM). If the exhaust is restricted, some exhaust can pass, and the effect may not be noticeable when the engine is at idle speed. However, when the engine is operating at a higher speed, the exhaust gases can build up behind the restriction and eventually will not be able to leave the combustion chamber. When some of the exhaust is left behind at the end of the exhaust stroke, the resulting pressure in the combustion chamber reduces engine vacuum STEP 1 Attach a vacuum gauge to an intake manifold vacuum source. STEP 2 Start the engine. Record the engine manifold vacuum reading. The engine vacuum should read 17 to 21 in. Hg when the engine is at idle speed. STEP 3 Increase the engine speed to 2,500 RPM and hold that speed for 60 seconds while looking at the vacuum gauge. If the vacuum reading is equal to or higher than the vacuum reading when the engine was at idle speed, the exhaust system is not restricted. If the vacuum reading is lower than the vacuum reading when the engine was at idle speed, then the exhaust is restricted. Further testing will be needed to determine the location of the restriction. 4) Testing a catalytic converter for temperature rise - A properly working catalytic converter should be able to reduce NO x exhaust emissions into nitrogen (N) and oxygen (O 2 ) and oxidize unburned hydrocarbon (HC) and carbon monoxide (CO) into harmless carbon dioxide (CO 2 ) and water vapor (H 2 O). During these chemical processes, the catalytic converter should increase in temperature at least 10% if the converter is working properly. To test the converter, operate the engine at 2,500 RPM for at least two minutes to fully warm the converter. Measure the inlet and the outlet temperatures using an infrared pyrometer. Catalytic converter efficiency tests: 5) Oxygen level test- With the engine warm and in closed loop, check the oxygen (O 2 ) and carbon monoxide (CO) levels. A good converter should be able to oxide the extra hydrocarbons caused by the rapid acceleration If O 2 is zero, go to the snap-throttle test. If O 2 is greater than zero, check the CO level. If CO is greater than zero, the converter is not functioning correctly. 6) Snap-throttle test: With the engine warm and in closed loop, snap the throttle to wide-open throttle (WOT) in park or neutral and observe the oxygen reading: The O 2 reading should not exceed 1.2%; if it does, the converter is not working. If the O 2 rises to 1.2%, the converter may have low efficiency. If the O 2 remains below 1.2%, then the converter is okay.

A catalytic converter has to be at least how hot before it starts to work? a. 500°F (260°C) b. 1,000°F (540°C) c. 1,500°F (815°C) d. 2,000°F (1,100°C)

A

The switching valves on the AIR pump have failed several times. Technician A says that a defective exhaust check valve could be the cause. Technician B says that a leaking exhaust system at the muffler could be the cause. Which technician is correct? a. Technician A only b. Technician B only c. Both Technicians A and B d. Neither Technician A nor B

A

Two technicians are discussing catalytic converters. Technician A says that the exhaust mixture must fluctuate between rich and lean 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? a. Technician A only b. Technician B only c. Both Technicians A and B d. Neither Technician A nor B

A

When checking for the proper operation of the AIR system using an exhaust gas analyzer, how much should the oxygen (O 2 ) levels increase when the pump is allowed to function? a. 1% to 4% b. 5% to 10% c. 10% to 20% d. Up to 30%

A

Where is the output of the AIR pump directed when the engine is cold? a. Exhaust manifold b. Catalytic converter c. Air cleaner assembly d. To the atmosphere

A

What does the abbreviation AIR mean?

Air injection reaction

A catalytic converter is being tested with an infrared pyrometer. Which is an acceptable (good converter) result? a. The inlet should be hotter than the outlet by 10%. b. The outlet should be hotter than the inlet by 10%. c. Both the inlet and the outlet should be the same temperature after the converter reaches operating temperature. d. The temperature of a catalytic converter is the best test to perform to locate a restricted (clogged) unit.

B

Technician A says that if a PCV valve rattles, then it is okay and does not need to be replaced. Technician B says that if a PCV valve does not rattle, it should be replaced. Which technician is correct? a. Technician A only b. Technician B only c. Both Technicians A and B d. Neither Technician A nor B

B

Technician A says that the PCV system should create a slight pressure in the crankcase at idle. Technician B says that the PCV system should create a slight vacuum in the crankcase at 2,500 RPM. Which technician is correct? a. Technician A only b. Technician B only c. Both Technicians A and B d. Neither Technician A nor B

B

Two technicians are discussing exhaust check valves used in SAI systems. Technician A says that they are used to prevent the output from the SAI pump from entering the intake manifold. Technician B says the check valves are used to keep the exhaust from entering the AIR pump. Which technician is correct? a. Technician A only b. Technician B only c. Both Technicians A and B d. Neither Technician A nor B

B

What is applied to the ceramic substrate to make the surface porous? a. Honeycomb filler b. Washcoat c. Aluminum d. Cerium

B

What two primary sensors does the PCM use to check the catalytic converter? a. Catalytic converter temperature sensor and rear oxygen sensor b. Precat and postcat oxygen sensor c. Precat oxygen sensor and MAF d. MAP and TP

B

Which exhaust gas reading indicates a good catalytic converter? a. O 2 is zero c. Both a and b b. CO is zero d. Neither a nor b

B

Technician A says that if the PCV valve was defective or clogged, the engine could idle rough. Technician B says that the engine may stall. Which technician is correct? a. Technician A only b. Technician B only c. Both Technicians A and B d. Neither Technician A nor B

C

Technician A says that the catalytic converter is warranted for eight years or 80,000 miles, 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? a. Technician A only b. Technician B only c. Both Technicians A and B d. Neither Technician A nor B

C

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 2,500 RPM for 60 seconds. Technician B says that a pressure gauge can be used to check for back pressure. Which technician is correct? a. Technician A only b. Technician B only c. Both Technicians A and B d. Neither Technician A nor B

C

A P0422 (catalytic converter efficiency failure) is set. What is a possible cause? a. Engine mechanical fault b. Exhaust leak c. Fuel contamination d. Any of the above

D

A catalytic converter can be harmed by ______________ . a. Excessive engine oil b. Antifreeze c. Sulfur from poor-quality fuel d. Any of the above

D

How much of the air needed by the engine flows through the PCV system when the engine is at idle speed? a. 1% to 3% b. 5% to 10% c. 10% to 20% d. Up to 30%

D

The PCV system controls which exhaust emission(s)? a. HC b. CO c. NO X d. Both HC and CO

D

The SAI system is used to reduce which exhaust emission(s)? a. HC b. CO c. NO X d. Both HC and CO

D

How does a catalytic converter reduce NOx to nitrogen and oxygen?

Exhaust gas passes through the catalyst, oxides of nitrogen (NO x ) are chemically reduced (that is, nitrogen and oxygen are separated) in the first section of the catalytic converter.

How does the computer monitor catalytic converter performance?

It uses a heated oxygen sensor (HO2S) both before and after the converter. With OBD-II-equipped vehicles, catalytic converter performance is monitored by a heated oxygen sensor (HO2S) both before and after the converter. SEE FIGURE 28-5 . The converters used on these vehicles have oxygen storage capacity (OSC), due mostly to the cerium coating in the catalyst rather than the precious metals used. When the three-way converter (TWC) is operating as it should, the post-converter HO2S is far less active than the pre-converter sensor. The converter stores, then releases, the oxygen during normal reduction and oxidation of the exhaust gases, smoothing out the variations in oxygen being released. Where a cycling sensor voltage output is expected before the converter, because of the converter action, the post-converter HO2S should read a steady signal with little fluctuation.

What exhaust emissions do the PCV valve and the SAI system control?

PCV systems help reduce HC and CO emissions. SAI system helps reduce HC and CO as well.

What does the abbreviation PCV mean?

Positive crankcase ventilation

How does a PCV valve work?

The PCV valve in most systems is a one-way valve containing a spring-operated plunger that controls valve flow rate. The flow rate is determined by the size of the plunger and the holes inside the valve. When manifold vacuum is high (at idle, cruising, and light-load operation), the PCV valve restricts the airflow to maintain a balanced air-fuel ratio. Under high speed or heavy loads, the valve opens and allows maximum airflow.

Why must a catalytic converter be mounted close to the exhaust ports of the engine?

To warmup quickly and be active as soon as possible after engine start-up since the catalytic converter doesn't work when it's cold.