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Testing exhaust gas recirculation valve N18 > < Hose layout plan for charge pressure regulation, exhaust gas recirculation valve and intake manifold flap

Octavia Mk1

Testing exhaust gas recirculation
Testing exhaust gas recirculation
The function of the exhaust gas recirculation is checked via the drawn in air mass. If the exhaust is guided back, the fresh air share detected by the air mass meter is less. The greater the exhaust gas recirculation rate, the smaller the signal from the air mass meter.
Special tools and workshop equipment required
t  Vehicle system tester -V.A.G 1552- with cable -V.A.G 1551/3, 3A, 3B oder 3C-
Test sequence for vehicles ? 07.97
–  Read measured value block, display group 001, engine at idling speed → Chapter.
   
–  Readout on display:
–  Check display in display field 4 (coolant temperature).
Specified value: min. 85°C
Only proceed with test once the coolant temperature has been reached.
–  Press the button C.
–  Enter 003 for the “display group number” and confirm with key Q.
  
Reading measured value block 1     ->
900/min    6.5 mg/s    1.480 V   87.3 °C
–  Readout on display:
–  Press the accelerator pedal briefly and then run the engine at idling speed.
  
Reading measured value block 3     ->
900 rpm    272 mg/s    268 mg/s      54%
–  Observe display in display field 2 (nominal air mass).
Specified value: 230...370 mg/s
If the nominal air mass is higher, this may be due to the following causes:
t  Coolant temperature too low.
t  Intake manifold temeperature very high.
t  Injection rate too high.
t  Fault in fault memory.
  
Reading measured value block 3     ->
900 rpm    272 mg/s    268 mg/s      54%
–  Observe display in display field 3 (actual air mass).
Specified value: Corresponds with nominal air mass in display field 2 (tolerance ± 20 mg/s)
If the current air mass is more than 20 mg/s lower than the nominal air mass, this may be due to the following faults:
t  Unmetered air in suction area.
t  Too much exhaust gas recirculation.
If the current air mass is more than 20 mg/s higher than the nominal air mass, this may be due to the following faults:
t  Engine running at idling speed since 3 minutes.
t  Too little or no exhaust gas recirculation.
If the actual air mass is a constant 425 mg/s, the following faults are possible:
t  Line interruption to air mass meter.
t  Implausible air mass detected.
If the specified values are not reached:
–  Initiate the final control diagnosis and actuate the exhaust gas recirculation valve → Chapter.
  
Reading measured value block 3     ->
900 rpm    272 mg/s    268 mg/s      54%
Readout on display:
The valve must click.
If the valve does not click:
–  Testing exhaust gas recirculation valve -N18- → Chapter.
If the valve does click:
–  Inspect vacuum piping → Chapter.
If vacuum piping is o.k.:
–  Testing mechanical exhaust gas recirculation valve → 1.9 ltr./81 kW Engine, Mechanics → Rep. Gr.26.
Test sequence for vehicles 08.97 ?
Checking the exhaust gas recirculation occurs in function 04 (basic setting). The exhaust gas recirculation valve is pulsed every 10 seconds so that the extreme values for the exhaust gas recirculation can be read off. These values are displayed in measured value block, display group 003, display field 3.
–  Connect vehicle system tester V.A.G 1552, engine runs in idle → Chapter.
–  Select function 04 “System in basic setting” and enter the display group number 003.
  
Actuator diagnosis                    ->
Exhaust gas recirculation valve -N18
The display in display field 2 must switch between EGR not active and EGR active every 10 seconds.
The readouts in display field 3 and 4 must vary within the following control range:
EGR not active
   Specified value in display field 3: 420...560 mg/s
   Specified value in display field 4: 0…5%
EGR active
   Specified value in display field 3: 170...340 mg/s
   Specified value in display field 4: 95…100%
  Note
If display field 3 displays a constant value of 550 mg/s, inspect the air mass meter → Chapter.
If the specified value is not reached:
–  Testing mechanical exhaust gas recirculation valve → 1.9 ltr./81 kW Engine, Mechanics → Rep. Gr.26.
–  Inspect vacuum piping → Chapter.
–  Testing exhaust gas recirculation valve -N18- → Chapter.
  
System in basic setting 3        ->
900 rpm  EGR not active    500 mg/s     0 %

Testing exhaust gas recirculation valve N18 > < Hose layout plan for charge pressure regulation, exhaust gas recirculation valve and intake manifold flap