chapter 84
when combustion flame temperatures exceed _______________°F NOx is formed inside the cylinder
2,500
digital EGR valves use
3 solenoids controlled by the PCM
on a EGR test how much should the vacuum drop
6 to 8 in Hg
When testing an EGR system for proper operation using a vacuum gauge, how much should the vacuum drop when the EGR is commanded on by a scan tool? 1 to 2 in. Hg 3 to 5 in. Hg 6 to 8 in. Hg 8 to 10 in. Hg
6 to 8 in. Hg
the EGR system routes small quantities usually between _________________ of exhaust gas into the intake manifold
6% and 10%
digital EGR valves can produce how many different flow rates
7
linear EGR valve has a
three wire potentiometer
digital EGR valves do not use
vacuum
would want EGR valve
warm engine off idle
positive back pressure EGR valves
without enough back pressure the EGR valve does not open
What causes the nitrogen and the oxygen in the air to combine and form NOx? Any spark will cause this to occur Sunlight Heat above 2500 degrees F (1370 degrees C) Chemical reaction in the catalytic converter
Heat above 2500 degrees F (1370 degree C)
EGR is used to control which exhaust emission? Oxides of nitrogen (NOx) Carbon monoxide (CO) Both NOx and CO Unburned hydrocarbons (HC)
Oxides of nitrogen (NOx)
A typical EGR pintle-position sensor is what type of sensor? Wheatstone bridge Piezoelectric Potentiometer Rheostat
Potentiometer
An EGR valve that is partially stuck open would most likely cause what condition? Rough idle/stalling Ping (spark knock or detonation) Missing at highway speed Excessive NOx exhaust emissions
Rough idle/stalling
EGR is used to lower
cylinder temperatures
oxygen in the exhaust ______________ when the EGR valve is open
decreases
signs the EGR valve is not opening
denotation excessive NOx
EGR helps prevent
denotation (uncontrolled combustion)
wouldn't want EGR valve
idle cold engine WOT
EGR system allows for greater ____________ advance
ignition timing
what is used on top of the EGR valve stem to indicate valve position to the PCM
linear potentiometer
exhaust gas recirculation (EGR) is an emission control system that
lowers the amount of nitrogen oxides formed during combustion
negative back pressure EGR valves
on each exhaust stroke the engine emits an exhaust pulse. allows it to open
many PCM controlled EGR systems have ____________ solenoids controlling the EGR vacuum
one or two
the PCM monitors either ________ or ___________ for a change in signal voltage
oxygen MAP sensor
linear EGR valves has a feedback
potentiometer that signals the PCM reguarding the actual position of the valve
linear EGR valves contain
pulse width modulated solenoid to precisely regulate exhaust gas flow
NOx creates a __________ colored haze that often hangs over major cities
red brown
if the EGR valve is stuck open
rough idle or frequent stalling poor performance/low power at low speeds
most PCM vacuum operated EGR systems use a
sensor to indicate EGR operation
digital EGR valve offers precise control using
swivel pintle
digital EGR helps prevent
carbon deposit problems
A P0401 DTC (exhaust gas recirculation flow insufficient) is being discussed. Technician A says that a defective EGR valve could be the cause. Technician B says that clogged EGR passages could be the cause. Which technician is correct? Technician A only Technician B only Both Technicians A and B Neither Technician A nor B
Both
OBD-II regulations require that the EGR system be tested. Technician A says that the PCM can monitor the commanded position of the EGR valve to determine if it is functioning correctly. Technician B says that the PCM can open the EGR valve and monitors for a change in the MAP sensor or oxygen sensor reading to detect if the system is functioning correctly. Which technician is correct? Technician A only Technician B only Both Technicians A and B Neither Technician A nor B
Both
Technician A says that a low-restriction exhaust system could prevent a back pressure-type vacuum-controlled EGR valve from opening correctly. Technician B says restricted exhaust can cause the EGR valve position sensor to fail. Which technician is correct? Technician A only Technician B only Both Technicians A and B Neither Technician A nor B
Both
Two technicians are discussing clogged EGR passages. Technician A says clogged EGR passages can cause excessive NOx exhaust emission. Technician B says that clogged EGR passages can cause the engine to ping (spark knock or detonation). Which technician is correct? Technician A only Technician B only Both Technicians A and B Neither Technician A nor B
Both
Exhaust gas recirculation (EGR) is generally not needed under all the following conditions EXCEPT: Cruise speed Idle speed Wide-open throttle (WOT) Cold engine
Cruise speed
excessive back pressure caused by a clogged exhaust system could cause
EGR valve to melt
fords use a EGR sensor called
Delta pressure feedback EGR (DPFE) sensor