VF check

[f00g00]

Well since my car is getting bad gas mileage I decided to check the VF signal.
Not sure if I did it right though;
I shorted T and E1 and had a meter on VF to battery ground.
At 2500 RPm the meter sits at .05 on 20V scale and doesn't move.
If I check it at idle and throttle up to 2500 it goes up to 5V one time them back to .05.
When I switch on the AC at 2500 RPM the system goes between 0 - 5V about 8 x in 10 seconds sometimes 0 - 3V in there as well.
any ideas?
I have my charcoal cannister running straight to the throttle body as my switch is broken on the thermostat housing.
Also the cap is off my AFM for the screw adjustment, don't know how to adjust that one either. I know what it does just don't know how to fine tune it.

 

[thevork]

Bad gas mileage is most probably due to a faulty O2 sensor.
Replace it if you didn't do that already.

Vf testing:

The Vf output has three different types of Vf output:

Oxygen sensor feedback mode
Diagnostic mode
Learned value mode
Oxygen sensor feedback mode

To test in this mode:

* Connect T and E1
* Make sure the idle contact point is Off (Note: this likely refers to the contact switch between pins 1 (E1) and 2 (FC) in the AFM -- jeff)
* Idle the engine at 2500 rpm

Result of oxygen sensor signal processing:

5V = rich

0V = lean

0v...........Open loop condition (Note: this was in the original text, but I'm not sure how it applies here. -- jeff)
Diagnostic mode

Your Vf can still be okay while your O2 sensor is failing. At least I had that.

Afm can only be tuned using a wideband sensor to check for perfect a/f values (14.7:1)

 

[jetjock]

With T and E shorted Vf outputs an emulated O2 sensor signal. The engine must be off idle. The idle contact referred to in the post above is the one in the TPS ie; "jeff" is mistaken.

At 2500 Rpm the meter sits at .05 on 20V scale and doesn't move. If I check it at idle and throttle up to 2500 it goes up to 5V one time them back to .05

That's not right. It should do what you say in the statement below. It does however show you have at least one trouble code stored. Check for it.

When I switch on the AC at 2500 RPM the system goes between 0 - 5V about 8 x in 10 seconds sometimes 0 - 3V in there as well.

That's what it should at 2500 rpm. The AC being on or off shouldn't matter. That said since AC on effects ignition timing you should also check that.

The screw on the 7MGE vane AFM is used to adjust idle mixture. Best to use some way of measuring A/F ratio but lacking that set it so Vf in the learned value mode is midrange (2.5 volts). The O2 sensor needs to be working to do this. Or set the screw where it was set at the factory. There's a code stamped into the AFM body that specifies where the screw was originally set.

 

[f00g00]

Put on a new Borg warner sensor that I ordered about 2 months ago, here is a pic with the borg next to the old Denso one. The Denso is the one that I tested the other day.
The Borg Warner just sits there and reads one time on the way up to 2500 and then just sits there at 0. It also doesn't idle up with AC on with the borg either so I put the old Denso back on. The Denso does.
The snout is also longer on the Denso which I think helps with the pace setter bung cause its slightly raised over stock.
I went with the borg cause I have an APO address so no UPS ground service here and it was the only one I could find that had someone willing to ship via US Postal service. I just went online and it turns out that Amazon has one that they are going to ship from their fullfillment center that was added 27 july 2007 so after I get that one I will test again.
I don't know if I just got a bad sensor or what but it goes to show that you should stick with OEM parts.

 

[f00g00]

I just checked the VF signal again with a new set of test leads (attatched photo) and the results are the same with the AC on it reads approx 8x between 0 and 5v in 10 seconds @ 2500 rpm. With the AC off it sits at 0 @ 2500 rpm but will read 5v one time as I throttle up to 2500 rpm from 0. At IDL they both read 0.
I have discovered though that with the AC off that it does test 8x in 10 seconds at any rpm off idle up to 2200 rpm. After that it flatlines back to 0 so Im guessing its testing good and the ecu for is cutting off the test @ 2200 for some reason.
The new test leads are a set of male pins from an old toyota plug that are an exact fit for the diagnostics plug. It is much better than my last lead which was a piece of .041 SS Safety wire, and it beats a paper clip any day.

 

[jetjock]

Again, if you have 0 volts on VF at idle you have a trouble code stored. Something is wrong though as AC shouldn't have any effect on the engine operating in closed loop. If I were you I'd check the O2 sensor directly instead of using Vf.

 

[twinturbozs]

How do you go about checking the oxygen sensor directly?