Fuel Mixture

EA1191 · 05-04-2007, 10:55 AM

There has been a sudden change in the reading of the Oxy sensor monitor.
This is the row of Leds which has been added to show the O2 output. It moves to the top (.8V - rich) and stays around there when cruising. Looks normal when climbing.
http://www.autozone.com/servlet/UiBr...3d8004f602.jsp
This site would claim that the O2 is faulty, but this has been a sudden change, maybe after adding lots of fuel to the tank.
No hoses have fallen off, the temp sensors and throttle position check OK. The diagnostic code is 11.
Any ideas or suggestions please.

CaRtZ · 05-04-2007, 11:02 AM

ur air to fuel should be 14.7:1 as on all engines (14.7 pound of air to 1 pound of fuel)...
a wire for the oxy sensor could have possibly worked loose or dirt/dust into the connection... but id say that yes, O2 sensor would be the problem...

webby_191189 · 05-04-2007, 11:13 AM

Quote:

Originally Posted by CaRtZ

ur air to fuel should be 14.7:1 as on all engines (14.7 pound of air to 1 pound of fuel)...
a wire for the oxy sensor could have possibly worked loose or dirt/dust into the connection... but id say that yes, O2 sensor would be the problem...

14.7:1 is the perfect ratio. Its not always going to be 14.7:1 due to weather, being under load, wear and tear ect..

ratter · 05-04-2007, 06:30 PM

Quote:

Originally Posted by webby_191189

14.7:1 is the perfect ratio. Its not always going to be 14.7:1 due to weather, being under load, wear and tear ect..

It should be 14.7 at all times if the O2 is working correctly, except when cold starting or when driving under acceleration

EA1191 · 06-04-2007, 10:48 AM

Is it easy to adjust the air/fuel ratio?
The fuel pressure is OK.
I will check the MAP when I think of someway to create a vacuum. Or just the normal air pressure may be enough. Pulled a pressure gauge apart and moved the needle to make it read vacuum.
Or just wait and see if all returns to normal. Thought that the fuel may have been 'diluted' (ethanol?) and the computer has not adjusted.

06-04-2007, 10:34 PM

if the map sensor was no good the motor will be hunting and blowing black smoke at idle
the perfect ratio is 14.7:1 bit most E.F.I systems run at 15:1 (Leaner) for emissions. i have played with cars other than falcons with the O2 sensor's i have found if you make a circuit board up with a series of resistors to step battery voltage down to about .74V they run well but it will stay at that all the time

ratter · 06-04-2007, 10:50 PM

14.7 is perfect for emission output only and is a compromise of power and slight economy.

Pretty much all EFI cars aim at getting that mixture under most driving conditions except for cars that use lean cruise mode. Lean cruise mode has pretty much disappeared the last few years as the nox gasses go up and do not meet the latest emission standards

The O2 sensor measure how much oxygen is in the exhaust and tells the ECU, which them adjusts the injectors to try to control the mixture to 14.7:1, so to adjust mixtures you need to recalibrate or trick the ECU

A faulty MAP sensor can also cause the motor to run lean as well as rich, so do not allways expect a faulty MAP to be causing running rough and black smoke, if it is disconnected from a vacuum signal it would be causing the motor to run rich as with no vacuum, the motor would think it was underload and pump more fuel into it.