EXCESSIVE FUEL CONSUMPTION

[CMF_Ian Smith]

Dear All
I recently purchased an immaculate 2001 Micra with only 26,000 miles on the clock, from a local dealer. The dealer provides a 3 month warranty and this runs out in about 4 weeks.
It has taken me a while to check the fuel figures and it seems that the vehicle is only returning 31 mpg. I had expected around 45 mpg.
Loking on this website and Honest John.co.uk (Daily Telegraph) one suggestion is a faulty mass airflow sensor and a 'choked' throttle body. In addition to the fuel problem the vehicle very slightly hesitates at 25mph on acceleration.
I feel I have come to right place for advice from other Micrafiles out there but I may have a fight with the garage! I hope not but it is difficult for the 'man in the street' to successfully argue on technical points!
Any suggestions would be appreciated.
Thanks
Ian Smith
ps incidently, I can recommend the Honest John website. He even mentions Alex B's repair to the throttle body.

 

[CMF_frank2]

hi ian, yours has the later bosch throttlebody, so the solder trick wont apply, (but you have the far cheaper, removable maf)
your best to get any faultcodes read first (small garage or ebay codereader) and then go from there

frank

 

[CMF_asdame]

i wonder if connecting the "12v" pin to the "check" pin on the diagnostic plug to put the ecu into diagnostic mode also works on a facelift micra frank? that's free if it works

also a faulty exhaust lambda sensor also makes it drink fuel cos the ecu has no feedback about the mixture so it goes into safe mode which results in a very rich mixture hence poor economy & performance.

the sensor could also be checked by the ecu diagnostic mode trick above then run the engine.

 

[CMF_frank2]

i cant find anything on autodata about self diag on the later eobd2 asdame, and i think the coilpack k11,s will flag up the mil light if one of the lambda,s fail
is it a stock 1.0 ian ?

frank

 

[CMF_asdame]

found this pic in msc for facelift obd2

ignition on
short the two pins for 2secs
then the eng light will flash the 1st fault code as long pulses followed by short pulses for the 2nd code number

code 55 = no faults logged

then start engine while in diag mode with the engine warmed up to test the lambda sensors working, eng light should blink bout every 1/2secs at 2000rpm.

 

[CMF_frank2]

thats obd1 asdame aint it (14 pin) his will be 16 pin type, with all the "P" codes

frank

 

[CMF_asdame]

ah ok

 

[CMF_Ian Smith]

Hi Both
Many thanks for the info. My Micra is the standard K11 first reg'd in March 2000.
My vehicle is fitted with the old style ECCS control unit that is accessed by removing the centre console. (Can see the picture makes sense now although I cannot read the text. Sorry but can you help me with this as I suspect this info will be useful) It was in July 2000 that Nissan fitted the diagnostic plug under the facia to the right of the steering column. I have found details of how to set up the diagnostic process in my Hanynes manual but will hold back from 'diving in' until the garage have had a go. At least they will not require any specialist equipment.
Thanks asdame for the tip about the lamba sensor. If this is faulty wouldn't the engine feel rough though? It runs sweet as anything. Maybe the plugs would provide an indication ie sooted up or clean honey colour?
Anyway, thanks again for your help with this. I am already unpopular with the garage as they sold it to me with 4 original tyres still fitted. The treads were fine but the walls were cracking and when I checked the dates they read 4/99. Everyone knows that tyres should be changed every five/six years regardless of the mileage. The garage refused to supply me with 4 new tyres so I had to pay for these myself.
Ian