Need some clarification on VF readings..

[Dragk913]

Ok, my car has been running pretty rich lately, so I checked the VF (using the Diagnostic box and a Multimeter).

On a 20v Scale, the multimeter read:
6.44v with the positive connected to E1
-2.44v with the positive connected to VF1

Does this mean the ECU is increasing the fuel input by 20%+ ?

or

Does it mean the ECU is decreasing the fuel input by 20%+ ?


According to the TSRM (when testing an O2 Sensor), you connect the positive to the VF1, but I wanted to make sure I wasn't just completely confused.


Thanks!


edit: The O2 Sensor was heated to operating temperatures, if that makes a difference.

 

[GrimJack]

This should be done on a 5v scale, it's going to be really tough to read on a 20v scale.

The ECU will output 5 steps on this, and they are all rather approximate - just round to the nearest step.

0v Reducing lots of fuel from base maps
1.25v Reducing some fuel from base maps
2.5v No change from base maps
3.75v Adding little bit of fuel from base maps
5v Adding lots of fuel from base maps

 

[Dragk913]

My (cheap) multimeter doesn't have a 5v scale:icon_frow...I guess I'll borrow a better one from a friend and redo the test.

Oh, and should I stick the positive probe on VF1 (like the TSRM says with checking the O2 Sensor)?

 

[GrimJack]

I don't recall which one was positive, to be honest. Doesn't matter with my meter, it just reads negative numbers if I get it wrong.

 

[Dragk913]

Alrighty, thanks a lot Grim!

 

[ForcedTorque]

Check out this link

http://racing.generationz.net/images/isnms/vffueltrim.jpg