EDIT: EA 3.9CFI 4spd auto

Not even 2 weeks ago i brought a brand new o2 sensor for repco, hoping that mine was stuffed, and was causing the 18l/100 fuel consumption. But it made no difference whatsoever..

So after reseting the ecu and giving it 2 weeks to run in it has not changed at all. Just for a test i disconnected the 02 sensor and the ISC started tthe car (dead cold) and took it for a bit of a spin.

The idle did not change one bit nor did the little metal bit at the end of the isc move, but it started to shoot out black smoke and use double the pettie (when looking at the instant Litres used) So i left the 02 sensor disconnected and plugged in the isc. Straight away the idle changed and the smoke was gone. Took it for a bit of a drive and noticed the instant litres used was back to normal.

So it looks as if the ecu is not reading the 02 sensor at all, as disconnecting it makes NO DIFFERENCE whatsoever to the fuel useage or running of the car.

I was just wondering which pins at the ecu connector should i be checking to see if the 02 sensor is reaching the comp? If anyone has access to a workshop manual, and could let me know of the acceptable working range at the wires (ohms, volts etc) that would be tops

If its the actual ecu, thats good as im going MPEFI soon enough.. but want to rule out a wiring problem before hand.

Cheers!

i was running my EF without the 02 connected for about a month and I was getting normal economy....I think its ok without it but if your sensor is f**k then the economy can go way out....

Had a similar problem a couple of weeks ago. Changed HEGO, MAP, ECT and ACT sensors all with little or no change. Changed whole of injection unit including injectors and problem got worse. After much tearing out of hair replaced injectors with new ones and petrol consumption dropped from approx 22L/100KMs to approx 13L/100KMs around town.

What KMs has your car done? If its over 300,000 or so may well be same problem. Check vacuum hose to MAP and wiring to temp sensors as well.

Output from HEGO is a low voltage which under normal running conditions will vary between approx 0.1 and 1.0 volts. See here for a better idea. http://fordfuelinjection.com/index.php?p=31

Hope this helps!!

Chris

look at that graph it shows that if the sensor is reading a low voltage then its indicating a lean condition....in that case the ecu will try to richen

so if your o2 sensor is rooted and only reading a low voltage your fuel consumption will rise....

Throw it on a dyno with a wideband o2 sensor plugged into the tailpipe, for one hours work and experimenting with various things on the motor you can save yourself dozens of hours of mucking around and wasted fuel.

is it getting to temp?

till it gets to ablut 80 odd degress it wont even use the sensor