EFI question

[j-top paj]

how important is the oxygen sensor in an efi car?? (patrol 4.5injected)

ive been having some minor probs with my patrol

http://www.outerlimits4x4.com/ftopic174603.php

and today when i was pulling the injectors out to get them cleaned etc.. i noticed that an earth strap on the heat shield for the exhaust manifold was loose/broken..
could it affect the oxygen sensor in the manifold??

[coxy321]

O2 sensors (A/F, lambda) are very important - as you probably arleady know, they basically tell the ECU what the fuel mixture is doing (rich or lean).

They can be a bit sensitive/temperamental - i'm pretty sure the 4.5 or 4.8 patrols actually had earthing issues on the oxy sensor which in turn created fuel consumption issues.

No idea about you earth strap, however the better the sensors earth is, the more effectively it will do its job.

[DamTriton]

Vehicles will run without O2 sensors, but they operate in "open loop" mode, meaning the ECU "guesstimates" the appropriate amount of fuel needed based on engine temp, revs, throttle position, etc. It does not get the feedback from the O2 sensors to allow it to fine tune the quantity of fuel required. Typically the designers make the ECU run rich when in open loop mode as there is not as much of an issue with keeping an engine running if it is rich as compared to one that is lean.

[lay80n]

The o2 sensor in older motors are usually just narrow band sensors. They are only used in closed loop mode to maintain a stoich mixture at low load cruise and idle situations. Once the motor see's any real load then the computer switches to open loop and runs pre-programed maps for the fueling and ignition. You can run without them fine, but your fuel consumption and response may suffer due to the computer running in open loop all the time.

Narrow band o2 sensors are only really useful around the 14.7:1 stoichometric (sp) point of a petrol motor. After about 14:1 or 15:1 there resolution is not acurate enough to determine a mixture. A mixture of 13.5:1 would barely show up different than a mixture of 12:1, yet the 13.5:1 would be bad for a turbocharged motor on boost while 12:1 will make safe power. This is why narrow bands are not very useful as a tuning tool, and why manufactures only use them on loaw load and idle situations. More and more modern cars are moving to wide band sensors that can acuratley read a much wider range of mixtures as a way of maintaining power levels whilst still achiving good economy and environmental restriction levels.

Yeah, i may be bored at work.

Layto....

[coxy321]

Would commodore's have narrow band O2 sensors? I would assume yes, up until the current VE where they have most likely gone to wide-band sensors.

Just curious because i need a new sensor for my Datto and the last one i got (Bosch Commodore one) was clearly not the right band for my gauge.