Your Path to ASE L1 Certification: Engine Performance
Expertise
Air fuel ratio (Very rich) 10.1 at all speeds
———- Idle Off idle Cruise
HC 250ppm 275ppm 300ppm
CO 3%. 3%. 3%
CO2 7 to 9 all down
O2 .2% all down
What can the possible cause be ?
A. Leaking injector
B. High Map sensor voltage (low pressure reading) (vacuum leak)
C. Stuck open thermostat
D. All the above - correct answer ✔✔D
Air fuel ratio (Rich) 10.1 to 12.1 at low speed
————Idle —-Off idle —-Cruise
HC —-150ppm —150ppm ——-100ppm
CO ——-1.5%. ———1.5%. ———-1.5%
CO2— 7 to 9% —7 to 9% ——11 to 13%
O2 —- .5% ——-.5% ———- 1.0
High Map sensor (vacuum leak)
Leak injectors
,Engine oil diluted with gasoline
Excessive crankcase blowby
Stuck open thermostat
And....
What else can cause this condition?
A. Low fuel pressure
B. Bad camshaft
C. High fuel pressure
D. All the above - correct answer ✔✔C
Air fuel ratio very lean above 16.1 at all speeds
————Idle —-Off idle —-Cruise
HC —-200ppm —205ppm ——-250ppm
CO ——-.5%. ———.5%. ———-1.0%
CO2— 7 to 9% —7 to 9% ——7 to 9%
O2 —- 4-5% ——-4-5% ———- 4-5%
Intermittent ignition problems (misfire)
Restricted fuel injector
Low fuel pressure
Vacuum leak
Improper timing
And..
What else could cause this concern?
A. Stuck open thermostat
B. Stuck close thermostat
,C. Both b and d
D. Low cylinder compression - correct answer ✔✔C
Air fuel ratio very lean above 16.1 at high speed
————Idle —-Off idle —-Cruise
HC —-100ppm —80ppm ——-50ppm
CO ——-2.5%. ———1.0%. ———-.8%
CO2— 7 to 9% —7 to 9% ——7 to 9%
O2 —- 2-3% ——-2-3% ———- 2-3%
Intermittent ignition problem (misfire)
Restricted fuel injector
Low fuel pressure
Vacuum leak
And
What else can cause this condition?
A. Heated air intake stuck in cold-air position
B. Bad map sensor
C. Incorrect timing
D. Bad throttle body - correct answer ✔✔A
Normal 13.1 to 15.1 emission chart
————Idle —-Off idle —-Cruise
HC —-100ppm —80ppm ——-50ppm
CO ——-.3%. ———.3%. ———-.3%
, CO2— 10 to 12% —10 to 12% ——10 to 12%
O2 —- 2.5% ——-2.5% ———- 2.5%
What is the cause for these reading ?
A. Faulty throttle body
B. Engine too cold
C. Engine too hot
D. Fails APP sensor - correct answer ✔✔B
HC- moderate increase
CO- large increase
CO2- some decrease
O2- some decrease
NOx- some decrease
What is the condition ?
A. Lean mixture
B. Rich mixture
C. Ignition misfire
D. Advance timing - correct answer ✔✔B
What can higher the emissions for NOx
A. Too much advance timing
B. Stuck close EGR valve
C. Cooling system problems
D. All the above - correct answer ✔✔D
Expertise
Air fuel ratio (Very rich) 10.1 at all speeds
———- Idle Off idle Cruise
HC 250ppm 275ppm 300ppm
CO 3%. 3%. 3%
CO2 7 to 9 all down
O2 .2% all down
What can the possible cause be ?
A. Leaking injector
B. High Map sensor voltage (low pressure reading) (vacuum leak)
C. Stuck open thermostat
D. All the above - correct answer ✔✔D
Air fuel ratio (Rich) 10.1 to 12.1 at low speed
————Idle —-Off idle —-Cruise
HC —-150ppm —150ppm ——-100ppm
CO ——-1.5%. ———1.5%. ———-1.5%
CO2— 7 to 9% —7 to 9% ——11 to 13%
O2 —- .5% ——-.5% ———- 1.0
High Map sensor (vacuum leak)
Leak injectors
,Engine oil diluted with gasoline
Excessive crankcase blowby
Stuck open thermostat
And....
What else can cause this condition?
A. Low fuel pressure
B. Bad camshaft
C. High fuel pressure
D. All the above - correct answer ✔✔C
Air fuel ratio very lean above 16.1 at all speeds
————Idle —-Off idle —-Cruise
HC —-200ppm —205ppm ——-250ppm
CO ——-.5%. ———.5%. ———-1.0%
CO2— 7 to 9% —7 to 9% ——7 to 9%
O2 —- 4-5% ——-4-5% ———- 4-5%
Intermittent ignition problems (misfire)
Restricted fuel injector
Low fuel pressure
Vacuum leak
Improper timing
And..
What else could cause this concern?
A. Stuck open thermostat
B. Stuck close thermostat
,C. Both b and d
D. Low cylinder compression - correct answer ✔✔C
Air fuel ratio very lean above 16.1 at high speed
————Idle —-Off idle —-Cruise
HC —-100ppm —80ppm ——-50ppm
CO ——-2.5%. ———1.0%. ———-.8%
CO2— 7 to 9% —7 to 9% ——7 to 9%
O2 —- 2-3% ——-2-3% ———- 2-3%
Intermittent ignition problem (misfire)
Restricted fuel injector
Low fuel pressure
Vacuum leak
And
What else can cause this condition?
A. Heated air intake stuck in cold-air position
B. Bad map sensor
C. Incorrect timing
D. Bad throttle body - correct answer ✔✔A
Normal 13.1 to 15.1 emission chart
————Idle —-Off idle —-Cruise
HC —-100ppm —80ppm ——-50ppm
CO ——-.3%. ———.3%. ———-.3%
, CO2— 10 to 12% —10 to 12% ——10 to 12%
O2 —- 2.5% ——-2.5% ———- 2.5%
What is the cause for these reading ?
A. Faulty throttle body
B. Engine too cold
C. Engine too hot
D. Fails APP sensor - correct answer ✔✔B
HC- moderate increase
CO- large increase
CO2- some decrease
O2- some decrease
NOx- some decrease
What is the condition ?
A. Lean mixture
B. Rich mixture
C. Ignition misfire
D. Advance timing - correct answer ✔✔B
What can higher the emissions for NOx
A. Too much advance timing
B. Stuck close EGR valve
C. Cooling system problems
D. All the above - correct answer ✔✔D
