Question 1

Technician A says that the air cleaner assembly has a bypass valve that allows air into the engine when the air filter is clogged. Technician B says that most air filters are mounted after the MAF. Who is correct?

Accepted Answer

Air cleaner assemblies typically do not have a bypass valve for when the air filter is clogged, as this would allow unfiltered air into the engine. Additionally, most air filters are mounted before the Mass Air Flow (MAF) sensor to ensure that the air entering the engine is measured accurately.

Question 2

All of the following are true about turbochargers EXCEPT ____.

Accepted Answer

Turbochargers typically provide maximum horsepower increase at higher RPMs, rather than just above idle. Therefore, statement C is false. Statements A, B, and D are all true.

Question 3

Faulty turbochargers can cause excessive amounts of oil to be leaked into the exhaust system.

Accepted Answer

Faulty turbochargers can cause oil leaks into the exhaust system due to worn out seals, damaged bearings, or other internal damage.

Question 4

Which of the following would be considered a vacuum at sea level?

Accepted Answer

A vacuum is defined as a space with a pressure lower than the atmospheric pressure at sea level, which is approximately 14.7 psia. Therefore, 12 psia, being below 14.7 psia, is considered a vacuum.

Question 5

A digital pyrometer is used to measure the amount of oxygen and carbon monoxide in the exhaust system.

Accepted Answer

A digital pyrometer is used to measure temperature. To measure the amount of oxygen and carbon monoxide in the exhaust system, a gas analyzer or an exhaust gas analyzer is used.

Question 6

Some air cleaner assemblies have a flow restriction indicator that indicates when the air filter needs servicing.

Accepted Answer

Some air cleaner assemblies have a flow restriction indicator that shows when the air filter requires servicing.

Question 7

Technician A says that an engine developing 10" of vacuum at idle is a normal condition. Technician B says that engines with clogged exhaust systems will have more than 20" of vacuum when under throttle. Who is correct?

Accepted Answer

An engine developing only 10" of vacuum at idle indicates a problem, as normal vacuum readings at idle are typically around 17-22 inches of mercury (Hg). Engines with clogged exhaust systems will not have more than 20" of vacuum under throttle; instead, they may exhibit decreased vacuum due to the restricted exhaust flow.

Question 8

Turbochargers are driven by a belt attached to the crankshaft of the engine.

Accepted Answer

Turbochargers are not driven by a belt attached to the crankshaft. They are driven by exhaust gases from the engine.

Question 9

1999 and new model year cars have sensors to indicate the efficiency of the catalytic converter.

Accepted Answer

The answer of 1999 and new model year cars have...

Question 10

Turbochargers are being discussed. Technician A says that the engine supplies oil to the turbocharger for lubrication. Technician B says that all turbochargers have coolant lines from the engine attached to prevent overheating. Who is correct?

Accepted Answer

Technician A is correct because turbochargers typically use engine oil for lubrication. Not all turbochargers have coolant lines; some rely solely on oil for cooling.

Question 11

Propane can be used to locate the sources of vacuum leaks.

Accepted Answer

Propane can be used as a test gas to locate the sources of vacuum leaks in an engine. When propane gas is introduced to the engine's intake system, it will be pulled into any areas where there is a vacuum leak, causing a change in the engine's idle speed or RPM. This method is commonly used by mechanics to quickly locate and diagnose vacuum leaks.

Question 12

Technician A says that intercoolers are used in turbocharger systems to cool the turbo bearings. Technician B says that some intercoolers are water cooled. Who is correct?

Accepted Answer

Intercoolers are used to cool the air compressed by the turbocharger, improving its density for better combustion, not for cooling turbo bearings. Some intercoolers are indeed water-cooled, making Technician B correct.

Question 13

Dirty air filters should be cleaned with compressed shop air to restore original air flow.

Accepted Answer

Cleaning dirty air filters with compressed air can damage the filter media, leading to reduced efficiency and potentially allowing harmful particles to enter the engine or HVAC system.

Question 14

An air leak in the ductwork between the MAF sensor and the throttle plate could cause an engine to run too lean.

Accepted Answer

An air leak between the MAF sensor and the throttle plate can cause extra air to enter the engine, which will not be accounted for by the MAF sensor. This will result in an incorrect air/fuel ratio and cause the engine to run too lean.

Question 15

Many intake system air ducts use a resonator to reduce noise generated within the ducts.

Accepted Answer

Air duct resonators are commonly used to reduce noise generated within the ducts. They work by creating an acoustic trap that absorbs and dissipates the sound waves traveling through the duct, reducing the amount of noise that makes it out of the duct and into the passenger cabin or surrounding environment.

Question 16

Intake manifolds on engines may be made of plastic.

Accepted Answer

Intake manifolds on engines can be made of plastic, as well as metal and other materials.

Question 17

Turbochargers are being discussed. Technician A says that the compressor wheel is mounted in the air intake system. Technician B says that boost pressure is limited by the wastegate. Who is correct?

Accepted Answer

Both technicians are correct. The compressor wheel is indeed mounted in the air intake system, and boost pressure is indeed limited by the wastegate. The compressor wheel compresses the air that enters the engine, which increases its density and allows for more oxygen to be burned during combustion. The wastegate controls the amount of exhaust gas that enters the turbocharger, which in turn controls the speed of the turbine and the amount of boost pressure produced by the compressor wheel.

Question 18

Technician A says that vacuum is high when engine load is high. Technician B says that vacuum is high when an engine is at idle speed and no load. Who is correct?

Accepted Answer

Technician B is correct. When an engine is at idle speed and no load, there is less air entering the engine, which increases the vacuum. When the engine load is high, there is more air entering the engine, which decreases the vacuum.

Question 19

Technician A says that engines with multi-port fuel injection use plastic intake manifolds to cool the air-fuel mixture. Technician B says that intake runners that are short and large in diameter are designed for peak power at lower engine rpm. Who is correct?

Accepted Answer

Plastic intake manifolds are used for weight reduction and cost efficiency, not specifically for cooling the air-fuel mixture. Short and large diameter intake runners are designed for peak power at higher engine rpm, not lower.

Question 20

Technician A says that engine vacuum is used to operate some emissions control devices. Technician B says that an EGR valve may be operated by engine vacuum. Who is correct?

Accepted Answer

Both technicians are correct. Engine vacuum is used to operate many emissions control devices, such as the PCV valve and the vacuum advance on older cars. An EGR valve can also be operated by engine vacuum to let in exhaust gases back into the engine to reduce NOx emissions.

Quiz 7: Intake and Exhaust Systems