VEC2 log of stock O2 sensors

[Ted Bigham]

Hi everyone. Good to be back on this site after some time away.

I'm pretty sure I have a bad O2 sensor. I'm trying to figure out which one based of my VEC2 log. They are definatly different from each other...

As you can see, one is fairly flat at idle, and the other is very "jittery". I know stock O2 sensors are supposed to pulse back and forth several times per second, but i'm not sure how much.

By the way, this is to try to figure out why my '94 stalls during idle unless I give it some gas.

 

[01bee]

How did you go about hooking up your O2 sensors to the VEC2?

 

[Casey]

Bring it to the dealer and have them see what code it's throwing and you'll be set!

 

[Sean Roe]

Bank 2 is the normal looking one.
Bank 1 is not changing voltage fast enough and is changing too little.
From the looks of the voltage output, the PCM probably thinks that bank is lean and is adding fuel.
That's about what one looks like when leaded race gas has been run in it and the lead starts to coat the sensor.
Ultimately, the PCM will set a check engine light for a lean mixture code as indicated by an abnormally rich correction factor.
New Bosch (direct plug in) sensors are about $70 at Napa, compared to about $120 from the Dodge dealer.
Regards,
Sean

 

[Tom F&L GoR]

Let me add to Sean's comment about "ultimately." I also have a OBD-1 '94. The factory check engine light does not illuminate until the system sees many continuous seconds worth of no or bad signal. Plugging it in at the dealer to look for stored codes therefore wouldn't tell you, unless they plug it in and watch the live signal. One tech said it's about 8 seconds; I believe it. Both my O2 sensors were bad, but because they did something "active" within the 8 second window, the MIL never came on. It does argue to change O2 sensors on a preventative schedule for OBD-1 systems; OBD-2 I suspect will tell you right away if one isn't working.

 

[Ted Bigham]

Thanks Sean. I have a wideband I've yet to hook up, so I guess I know which side it's going into now.

Casey, no circuit trouble code gets thrown. I think that only happens if the voltage moves too far, or not at all. A rich condition code gets thrown (plus some obvious backfiring)

O1bee, I tapped right into wires near the computer. I don't know the pin numbers off-hand, and they probably wouldn't match an '01 anyway. But if anyone really want's them I can look it up real quick. I recommend logging the throttle position too unless you're only tuning WOT. Sometimes the graphs don't seem to make sense wihtout it. You also get an ACTUAL response time measurement.

What I'd REALLY like to see (Sean), is for the VEC2 to be able to use the throttle position sensor (or TPS delta) as a factor in fuel delivery, so when I go let off the gas real fast (at low speed), it can cut more fuel eliminate that ever so popular exhaust explosion.

 

[01bee]

Thanks Ted, does anyone know what pin numbers I need to tap into for my O2 sensors to hook them up to the VEC2. Do you just hook them up to the analog in?

 

[Ted Bigham]

Yes, you just hook them up to the analog in. I think my VEC2 came with a diagram of the Viper's computer connections. Are you sure yours didn't?

 

[01bee]

Don't know I had a tech do the install, I will have to go take a look at the manuals.