air/fuel ratio

[Ryan]

I had a fuel/air guage fitted to my 97 legacy GTB to try and trouble shoot
my fuel economy problems and found that 90% of the time it is running rich,
this looks to be the reason behind my poor fuel economy (14L/100km). Can
anybody tell me what my first step should be to help bring this back to a
resonable ratio?

cheers

Ryan

 

[The Masked Marvel]

Check your oxygen sensor. Failed sensor will run rich.

 

[MIKE]

Check the rear o2 sensor (after the catalytic converter) on the down pipe
runing off the turbo
Sometimes they become unplugged if they snag or shake loose. Or if there is
a aftermarket downpipe the muffler shop forget to fit it or break it.
Where did you hook up the air/fuel gage to? the front o2 sensor?
How much $NZ did it cost?
I'm looking to do the same but my I'm using 8.7-12l/100km.
Mike

 

[Ryan]

I think it cost about $120. I didn't hook it up myself, I got an installer
to do it, I'm not certain where it is connected to, it ends up terminating
under the fuse box there somewhere. How will I know if my O2 sensor is
faulty. When I'm not pulling boost the guage goes sparaticlly between lean
and rich and doesn't stay still untill my boost pressure is above 0 psi, is
this typical of a A/F meter or is this a problem with the sensor?

 

[MIKE]

I just bought myself an a/f gauge, I'll tell you how it goes.

Anyway the instructions said that the a/f ratio should be rich when cold,
accelerating or while on boost. Driving at constant speed, decelerating or
idle it should be slightly lean.

The a/f meter should stay pretty much constant for contant conditions
described above.

for example while accelerating the af should read rich how rich may vary.



Have you reset the ECU - disconnect the battery overnight.

 

[Ryan]

how did the A/F go for you Mike??

I just bought myself an a/f gauge, I'll tell you how it goes.

Anyway the instructions said that the a/f ratio should be rich when cold,
accelerating or while on boost. Driving at constant speed, decelerating or
idle it should be slightly lean.

The a/f meter should stay pretty much constant for contant conditions
described above.

for example while accelerating the af should read rich how rich may vary.



Have you reset the ECU - disconnect the battery overnight.

 

[MIKE]

Not so good - I made the mistake of buying one of those DIY kits and the
stupid thing didn't work so know I have to fault-find which takes time that
I don't have at the moment.
-Mike