very poor TD5 mpg

Hi all,

my Disco Td5 auto has developed a real drinking problem. I've done the proper fill up, use, re-fill test and i'm getting 18.8mpg!

She gets used everyday, does a 40mile round trip on mainly A roads doing what i would call careful driving (no traffic light grand prix, rev's kept below 3000rpm etc)

there's no leaks anywhere and it's running fine. I do get the "air flow circuit <intermittent> fault show up on the nanocom (not sure why as it had a new one fitted late last year) but onced cleared normally stays a way for a week or so

Any ideas on why the mpg is so bad?

Flat tyres? Air filter / oil filter ? Massive roof box left open?!!!

sparkyspice said:

Flat tyres? Air filter / oil filter ? Massive roof box left open?!!!

Click to expand...

Nope! all pressures as they should be. K&N (clean), recently serviced. even polished it at the weekend to see if that would improve MPG!!!

Hi, This is Mclean from Todd and Mclean here Just joined so forgive any violations of landyzone etiquette!

I see you mentioned KN filter. I understand these filters are loaded with oil for particle entrapment and have read that this can contaminate the airflow meter. If the air flow meter is inaccurate then this could lead to poor fuel consumption. This may explain the periodic faults indicated with the airflow meter.

Airflow meters have a couple of wires one hot and one cold. Current is varied to maintain a constant temperature in each wire. The difference between them allows the ECU to calculate the speed and temperature of the air. Since the flows through a hole of the a known and fixed cross sectional area the ECU crunches the numbers to determine the mass of the air so can determine the best amount of fuel. As you might imagine it does not take a lot to knock out the calibration.

There is also a sensor in the standard airbox that measures the ambient air pressure for the same sort of reason ; to regulate the fuel. If this has been removed to fit the K&N or is out the air stream it will give a false reading.

getting the tracking done on mine increased my mpg by about 3 to the gallon.