Hey all!
I have a '94 Pick Up with 3VZE. I have my ThinkTool ProS hooked up to the OBD1 Diagnostic port under the hood.
This is what I am getting. I have some concerns. If anyone can help point me to information on learning more it would be appreciated.
Things Ive noticed:
Intake Manifold Pressure is to High. What does 3VZE use for manifold pressure sensor? I have not figured out yet...
R Air/Fuel Voltage is always zero and reading lean. This is the rear O2 sensor. R O2 sensor is always in open loop also.
The R O2 signal wire responds to testing and I am concerned with fuel delivery and that will be inspected next. But how is the 3VZE calculating manifold pressure?
My L O2 Sensor is switching really slowly also when I have it connected to my scope. I know that new O2 sensors switch at about 100ms. Mine takes the whole screen, about a whole second between switching rich/lean. Seems way to slow. Does anyone have ability to hook up a scope on 3VZE O2 signal wires for comparison? Or know what to expect on this old '94?
Ive included the Data Pids given to me on my scantool. Better pics next time...

 

I'm sure it's been done before, but this is the first time I've seen a scan tool used on the 3VZE. Pretty cool.

This engine uses the variable airflow meter at the air filter to set fuel requirements. No manifold pressure sensor anywhere on the engine. Definitely read up on the VAFM before tinkering with it, because many have been accidentally destroyed taking them apart.

The rear O2 sensor shouldn't see much if any change if the cat is working.

 

KOEO I am reading 70InHg. Drops to 50InHg @ idle.
Should be reading closer to 29InHg KOEO and 9InHg @ idle.
Whatever determines manifold pressure is off. Still reading on the VAFM. Does it determine manifold pressure engine off?
Second problem:
My R O2 is pegged lean around zero volts. Should be reading closer to straight line 450mv and 800mv with fuel. But it only reads 800mv when given propane.
I also think my front O2 sensor is switching to slowly. I would like to compare O2 signals on a scope with anyone if possible,

 

There is no manifold pressure signal in the diagnostics serial stream. So I don't know why your Think Tool thinks there is; perhaps it is trying to calculate it from something else?

Your Think Tool is showing screens for "L" and "R" Sensor Status and Air/Fuel. Do you have two front O2 sensors? I would be very surprised if a 3VZE ECM would support that.

The O2 sensor should switch 8 times (or more) in 10 seconds if working correctly. http://web.archive.org/web/201003261...01heatedox.pdf Why do you think yours is switching too slowly?

 

Yea, I'm just trying to make sense of what Im looking at. I couldnt find any info on manifold pressure, so thats why I asked. Must be calculated value. Its way off. I would expect that to increase injector pulse width and cause Rich O2 signal, but I am not seeing that....
I noticed the way Thinktool or Toyota has labeled the O2 sensors L and R. L sensor is the upstream sensor and there is only 1.
L O2 does go into Closed Loop. R O2 does not.
I had my scope hooked up to both O2 signal wires.
L O2 is only switching 1x per second instead of 8-10x/ second. So it appears to be switching very slow.

 

[QUOTE=scope103;52481014]... The O2 sensor should switch 8 times (or more) in 10 seconds if working correctly .../QUOTE]

8-10x in 10 seconds, not 1 second. 1x per second is right on the money. (Or, at least WNL.)

[I spent a few seconds on the interwebs to see if I could find someone saying that "new" o2 sensors switch 10x/second. I'm sure it varies by manufacturer, but all the "DIY" sites recommend watching for the switch on a voltmeter. You're not going to see 10 hertz switching on an instrument like that. But that doesn't matter; I've given you the correct number right from the horse's mouth.]