Deck 20: Fuel Trim Diagnosis

Question 1

If the air-fuel ratio is 14.7:1, what is Lambda?

A) 1.1
B) 0.9
C) 1.0
D) 14.7

Answer 1

C

Question 2

If Lambda is 0.98, this means the ________.

A) mixture is lean
B) air-fuel mixture is slightly rich
C) air-fuel mixture is within 2% of stoichiometric
D) Both B and C

Answer 2

D

Question 3

Base pulse width is determined by ________.

A) oxygen sensor data
B) computer calculations
C) input from many sensors, except the oxygen sensor
D) Both B and C

Answer 3

D

Question 4

The air at high altitude has ________.

A) Less than 21% oxygen
B) Higher pressure
C) Higher density
D) 21% oxygen

Question 5

The MAF sensor may give an inaccurate measurement if the ________ is modified.

A) AC system
B) cooling fan
C) radiator
D) air inlet system

Question 6

The catalytic converter is most efficient when the air-fuel mixture is ________.

A) at 14.7:1 air/fuel ration
B) at 1.0 lambda
C) varying from rich to lean (0.9 to 1.1 lambda)
D) Both A and B

Question 7

Injector pulse width is measured in ________.

A) milliseconds (mS)
B) duty cycle (%)
C) frequency (Hz)
D) percentage (%)

Question 8

What is NOT true about short-term fuel trim?

A) Able to react quickly to add or subtract fuel
B) Can add or subtract a large amount of fuel
C) Is expressed in percentages
D) Uses the oxygen sensor

Question 9

A Nissan vehicle is being checked using a scan tool and Alpha is 107. This means ________.

A) the PCM represents STFT only
B) the PCM represents LTFT only
C) the PCM is subtracting fuel
D) the PCM is adding fuel

Question 10

A contaminated or defective MAF sensor is indicated if ________.

A) the fuel trim numbers are within ± 2%
B) the fuel trim number follows the airflow
C) the BARO reading is lower than normal
D) the VE is bad

Question 11

In a speed density system, what does NOT needed to calculate base pulse width?

A) Amount of EGR
B) BARO sensor data
C) Air temperature
D) Oxygen in exhaust from the oxygen sensor

Question 12

In a MAF system, which of these statements is correct?

A) Altitude correction is needed.
B) The amount of EGR flow must be subtracted from the MAF sensor reading.
C) The temperature of the air correction is not needed.
D) The system measures the actual mass of the air entering the engine.

Question 13

Fuel trim provides a method that is capable of changing the amount of fuel delivered to the engine based on feedback from which of these input sensors?

A) Engine coolant temperature
B) Oxygen sensor(s)
C) TPS (Throttle Position Sensor)
D) MAF (Mass Air Flow)

Question 14

Technician A says that the primary purpose of fuel trim is to keep the air-fuel mixture as close to 14.7:1 as possible. Technician B says that when the air-fuel ratio is at 14.7:1, the efficiency of the catalytic converter is the lowest. Which technician is correct?

A) Technician A only
B) Technician B only
C) Both technicians A and B
D) Neither technician A nor B

Question 15

Technician A says that air-fuel ratio lambda numbers lower than 1.0 indicate a lean mixture. Technician B says that air-fuel ratio lambda numbers higher than 1.0 indicate a rich mixture. Which technician is correct?

A) Technician A only
B) Technician B only
C) Both technicians A and B
D) Neither technician A nor B

Question 16

To determine the air-fuel ratio if Lambda is given, multiply Lambda times ________.

A) 14.7
B) 1.47
C) 2.47
D) 0.47

Question 17

The equivalence ratio (ER) is ________ lambda.

A) 5% higher than
B) the same as
C) the inverse of
D) 5% lower than

Question 18

A Lambda of 0.97 means that the engine is operating ________ rich and has an air-fuel mixture of ________.

A) 13%; 15.7:1
B) 1%; 14.7:1
C) 0.3%; 14.1:1
D) 3%; 14.3:1

Question 19

Older fuel injection systems (multiport or gang-fired systems) were capable of providing an air-fuel mixture within an accuracy of about ________% of stoichiometric.

A) 4
B) 8
C) 6
D) 2

Question 20

The volumetric efficiency of an engine can be increased to more than 100% by use of ________.

A) 103 octane fuel
B) turbocharging
C) 5-valve cylinder heads
D) a second overdrive gear

Question 21

The primary purpose of the fuel trim is to keep the air-fuel mixture as close to ________ as possible.

A) One
B) Lambda
C) 14.7:1
D) Both B and C

Question 22

Fuel trim values can be read using ________.

A) a DMM
B) a scan tool
C) the driver information center
D) None of the above