Engine Performance SOS/ASE Exam
Questions & Answers (Grade A+)
What are the key components in an EVAP system? -
correct answer ✅Fuel Tank, gas cap, lines/hoses, and charcoal
canister
Catalytic Converter: -
correct answer ✅Oxidizes NOx into CO and HC
When testing a connector what is an acceptable reading?
a.) 1V from ground side
b.) 1V from positive/reference side
c.) .5V from at each connector
d.) 1.5v from sensor harness -
correct answer ✅C
An oxygen sensor is reading 400mv, what would this indicate -
correct answer ✅lean condition
What increases NOx emissions? -
correct answer ✅High combustion temperatures
,Engine Performance SOS/ASE Exam
Questions & Answers (Grade A+)
You have examined a set of spark plugs and found them to have a
black crusty finish on them. What does this indicate? -
correct answer ✅Rich air/fuel mixture
A vehicle comes in with poor performance, low power and a
flashing check engine light. What would this indicate? -
correct answer ✅Engine misfire
What is the function of the EGR valve? -
correct answer ✅to recirculate exhaust gases into the intake
Emission control systems are installed on engines to reduce what 3
specific exhaust emissions? -
correct answer ✅(HC) hydrocarbons, (CO) Carbon Monoxide, and
Oxides of Nitrogen (NOx)
You are monitoring the TPS/APP sensor voltage reading with slow
steady acceleration should read: -
correct answer ✅.50v at idle to 4.5 at WOT
,Engine Performance SOS/ASE Exam
Questions & Answers (Grade A+)
If the voltage reading on one cylinder is not high enough, what is
the most likely source of the problem? -
correct answer ✅Bad spark plug
At WOT the PCM module reverts to: -
correct answer ✅Open loop, rich mixture
What are the 2 types of EVAP Leaks? -
correct answer ✅0.020 small leak and 0.040 large leak
1.) All the following are pre-combustion emission controls except:
a.) Catalytic converter
b.) PCV system
c.) Timing control systems
d.) EGR systems -
correct answer ✅A
Tech A says that HCs result from unburned fuel and from
incomplete combustion.
Tech B says that CO is formed with a mixture that is too rich.
, Engine Performance SOS/ASE Exam
Questions & Answers (Grade A+)
Which Technician is correct? -
correct answer ✅Both
Port injection injects fuel: -
correct answer ✅Injects fuel behind the intake valve
(DI) Direct Injection: -
correct answer ✅Injects fuel directly into the combustion chamber
(Diesels)
What do post-combustion control systems do? -
correct answer ✅Cleans up exhaust gases after fuel has been
burnt
What does the downstream O2 sensor do? -
correct answer ✅monitors catalytic converter efficiency
Why is idle speed increased during a cold start?
a.) To prevent misfires
b.) To warm up the catalyst
c.) To make it easier to drive away
Questions & Answers (Grade A+)
What are the key components in an EVAP system? -
correct answer ✅Fuel Tank, gas cap, lines/hoses, and charcoal
canister
Catalytic Converter: -
correct answer ✅Oxidizes NOx into CO and HC
When testing a connector what is an acceptable reading?
a.) 1V from ground side
b.) 1V from positive/reference side
c.) .5V from at each connector
d.) 1.5v from sensor harness -
correct answer ✅C
An oxygen sensor is reading 400mv, what would this indicate -
correct answer ✅lean condition
What increases NOx emissions? -
correct answer ✅High combustion temperatures
,Engine Performance SOS/ASE Exam
Questions & Answers (Grade A+)
You have examined a set of spark plugs and found them to have a
black crusty finish on them. What does this indicate? -
correct answer ✅Rich air/fuel mixture
A vehicle comes in with poor performance, low power and a
flashing check engine light. What would this indicate? -
correct answer ✅Engine misfire
What is the function of the EGR valve? -
correct answer ✅to recirculate exhaust gases into the intake
Emission control systems are installed on engines to reduce what 3
specific exhaust emissions? -
correct answer ✅(HC) hydrocarbons, (CO) Carbon Monoxide, and
Oxides of Nitrogen (NOx)
You are monitoring the TPS/APP sensor voltage reading with slow
steady acceleration should read: -
correct answer ✅.50v at idle to 4.5 at WOT
,Engine Performance SOS/ASE Exam
Questions & Answers (Grade A+)
If the voltage reading on one cylinder is not high enough, what is
the most likely source of the problem? -
correct answer ✅Bad spark plug
At WOT the PCM module reverts to: -
correct answer ✅Open loop, rich mixture
What are the 2 types of EVAP Leaks? -
correct answer ✅0.020 small leak and 0.040 large leak
1.) All the following are pre-combustion emission controls except:
a.) Catalytic converter
b.) PCV system
c.) Timing control systems
d.) EGR systems -
correct answer ✅A
Tech A says that HCs result from unburned fuel and from
incomplete combustion.
Tech B says that CO is formed with a mixture that is too rich.
, Engine Performance SOS/ASE Exam
Questions & Answers (Grade A+)
Which Technician is correct? -
correct answer ✅Both
Port injection injects fuel: -
correct answer ✅Injects fuel behind the intake valve
(DI) Direct Injection: -
correct answer ✅Injects fuel directly into the combustion chamber
(Diesels)
What do post-combustion control systems do? -
correct answer ✅Cleans up exhaust gases after fuel has been
burnt
What does the downstream O2 sensor do? -
correct answer ✅monitors catalytic converter efficiency
Why is idle speed increased during a cold start?
a.) To prevent misfires
b.) To warm up the catalyst
c.) To make it easier to drive away
