Bad fuel consuption on K11

#1
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
#3
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
 
#4
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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