Bad fuel consuption on K11

Hello to all

My k11 (1998) had very bad fuel consumption ! 9.5L/km !! My Gti mkv with 20L turbo engine makes 10.3L/100km !!

Can anyone help my in order to check the possible causes ?

I had a multimeter so i think to start with testing the coolant & the lambda sensors
Can anyone advise me with the procedure to test them with the multimeter ?

Or any other checks to find out what is going wrong ?

My driving style is very good and smooth

Thanks
 

pollyp

Club Member
to check O2 to see if it's running closed loop and responding fast enough, warm up the engine fully then there's 4 ways to check the sensor:

Oscilliscope: a normal digital multimeter ain't responsive enough to show the O2 voltage oscilate twice a sec without a laggy blur of numbers.
preferably tap an oscilliscope into the signal wire and view the duty cycle of the sensor output at 2k rpm, should go up/down rich/lean bout twice/sec.
any slower and the sensor is getting worn.

Shorting diagnostic port: without any consult cable or oscilliscope, on most later generation micras you can set the ECU into diagnostic mode with a paperclip trick & looking at the engine light.
turn IGN on, using a paperclip you short the "Ign" & "Check" pin on the diagnostic plug by the drivers fuse box for 2sec then remove. pay careful attention to the pattern of the pin holes and dividing slots.

on pre-facelifts it's the lower left pins
post-62010-1240420944.jpg


on face-lifts it's upside down, the upper right pins
Untitled-1 copy.jpg


while engine's not running yet it's in diagnostic mode 1 and simply flashes any stored ECU codes via the engine light, long flashes = first number, short flashes = 2nd number.

to check the O2 sensor in diagnostic mode 2, start the warm engine and hold 2k. the engine light now represents the sensor, ON = lean, OFF = rich, should blink twice per sec.

laptop consult program: with a consult cable and free ECU diagnostic software or nissan datascan, switch IGN on, connect to the ECU, view sensor readings, warm up & hold 2k rpm and the primary O2 sensor should go rich/lean rapidly twice per sec

consult diagnostic device: same as the laptop but with a standalone device

To check ECU coolant sensor to see if it's reading too cold (high Ohm or disconnected) making it run a permanently cold rich mixture: remove the 2-pin temperature sensor, connect to a multimeter, dip in boiled water and log the resistance against degree C. Should match this
https://www.micra.org.uk/threads/pollymobiles-rebuild.35251/page-119#post-704079
 
to check O2 to see if it's running closed loop and responding fast enough, warm up the engine fully then there's 4 ways to check the sensor:

Oscilliscope: a normal digital multimeter ain't responsive enough to show the O2 voltage oscilate twice a sec without a laggy blur of numbers.
preferably tap an oscilliscope into the signal wire and view the duty cycle of the sensor output at 2k rpm, should go up/down rich/lean bout twice/sec.
any slower and the sensor is getting worn.

Shorting diagnostic port: without any consult cable or oscilliscope, on most later generation micras you can set the ECU into diagnostic mode with a paperclip trick & looking at the engine light.
turn IGN on, using a paperclip you short the "Ign" & "Check" pin on the diagnostic plug by the drivers fuse box for 2sec then remove. pay careful attention to the pattern of the pin holes and dividing slots.

on pre-facelifts it's the lower left pins
View attachment 44197

on face-lifts it's upside down, the upper right pins
View attachment 44198

while engine's not running yet it's in diagnostic mode 1 and simply flashes any stored ECU codes via the engine light, long flashes = first number, short flashes = 2nd number.

to check the O2 sensor in diagnostic mode 2, start the warm engine and hold 2k. the engine light now represents the sensor, ON = lean, OFF = rich, should blink twice per sec.

laptop consult program: with a consult cable and free ECU diagnostic software or nissan datascan, switch IGN on, connect to the ECU, view sensor readings, warm up & hold 2k rpm and the primary O2 sensor should go rich/lean rapidly twice per sec

consult diagnostic device: same as the laptop but with a standalone device

To check ECU coolant sensor to see if it's reading too cold (high Ohm or disconnected) making it run a permanently cold rich mixture: remove the 2-pin temperature sensor, connect to a multimeter, dip in boiled water and log the resistance against degree C. Should match this
https://www.micra.org.uk/threads/pollymobiles-rebuild.35251/page-119#post-704079
Thanks dude

I will check the above
 
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