Fuel Consumption Trebled O/Night

[CMF_uninformedLuddite]

I have lurked for a while but this is my first post as I have had no problems at all over the last 12 months with my $800 Micra.
I live in the Adelaide Hills and the car is driven over 1000km every week. Fuel consumption has been beautiful. The gauge rarely gets under a quarter as every time the tripmeter hits 300+ kms we put 20 litres of fuel in which works out to be 15km/l which seems Ok to me.
Just last week though it dropped to around 6.5km/l which seems to indicate something has gone wrong. Can anyone please suggest what could cause such a sudden in change in consumption basically overnight.

 

[CMF_nsm]

maybe oxygen sensor.....

 

[CMF_qwerty132]

any luck tracking down the reason??

Maybe the coolant temp sensor??

qwerty132

 

[CMF_nz_aj]

An o2 sensor would normally only make about a 10% difference.
Trebling of fuel consumption points first of all to MAF.
Temperature sensor is also a candidate.
I'd guess an $800 Micra has probably done plenty of km's & both of these (and the O2 sensor) are probably at the end of their lives. How many km's has it done?

 

[CMF_uninformedLuddite]

Sorry for the delay in my response. I ended up getting ecutalk to get a greater overall picture of whats happening. It was the lambda and that has been replaced and fuel economy is around 5.3l/100km(the average reported by ecutalk software) 60% country/40% city. I have a pretty heavy foot driving around town so that is I think a pretty good turnout.
As far as coolant goes when driving around the city the gauge sits around half and ecutalk reports around 80 degrees. As soon as it is in the country and sitting on around 90kmh the temperature rapidly drops to around 68 and stays there.
Not sure what an MAF actually is and as I have exceeded my 10GB monthly limit I am now at slower than dialup speed and it takes several miunuted for a page to load so can't really research what an MAF is. I had a friend do a compression test and that is fine too.
If I haven't mentioned elsewhere the car is a 1996 K11 with a CG13 engine. It has done about 150,000kms and has that horrible mottled paint job that the aussie sun causes. Also the left hand bolt hole in the front numper is broken so that means the bumper sticks out a bit and the nIssan logo on the back is missing. Still a great buy for $800 as we have done over 50,000km over the last year in it.

 

[CMF_uninformedLuddite]

Oh and having moved from a Toyota Landcruiser to a Nissan Micra and travelling a 1000km per week the car has paid for itself in fuel savings many times over. Every panel on the car is dead straight except for a small scratchy dent on the drivers rear which I will eventually fix up with a bit of spray putty and a can of paint.
I love my Micra.

 

[CMF_nz_aj]

MAF http://www.k11wiki.com/index.php?title=Throttlebody_/_MAF_/_Idle_control

You need to replace your thermostat. You'll save some more gas once you do. Running at these temperatures the fuel mixture will be rich. http://www.k11wiki.com/index.php?title=Thermostat

5.3L/100km (=18.87km/L=53.3mpg) is better than I'd expect and much better than I've ever achieved but Australia is pretty flat.

The 15km/l (=6.67L/100km=42.4mpg) you stated previously is about what I get if I drive nicely & not so much around town.