Olds 3.4L O2 sensor questions.

Good evening...
My girlfriends car has been giving her problems starting lately. It's a '00 Olds Alero with the 3.4L. 78,000 miles.
The car had something audibly wrong with the idle, but I couldn't pinpoint
it. It wasn't a clear miss, just and odd rythem to it... like an cammed motor hunting at idle.
I have some VCM editing software for my ls1 truck, that has a built in scanning tool for any GM OBDII vehicle. I'm able to view a LOT of the PID's that the computer monitors with a few different interfaces.
I hooked up my laptop to her car, and was very confused at what I saw.
Her Bank1 02 was responding very slow, compared to what I'm used to seeing with my bran-new '04 truck. I get a good 2-4 cycles in on average, to each one of her cycles. It was fluctuating between low voltages of 80mv, and high's of 880 or so. That's rather normal from what I understand.
Bank2 blew me away. I'm looking at a flatlined voltage of 8-26mv.
Long Term Fuel Trims: B1 = -9 on average. B2 = -75 hardlined. Short Term Fuel Trims: B1 = 0 on average. B2 = -50 hardlined.
Incredible. It looks like the motor shouldn't even be running.
So I start digging around the engine bay. I see an 02 sensor out back, on the rear banks manifold. But that's it. I don't see an 02 on the front bank. IS there a seperate 02 for each bank?
If there's not, that would explain the very strange data I'm seeing above.
Regardless, it looks like the B1 02 sensor is responding quite slow, so it's probably time that it gets replaced. What's the average lifespan for an 02 sensor?
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On Thu, 10 Jun 2004 22:21:52 -0400, "Marc Westerlind"

goofey readings (grin).
Regards, Al.
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Al Haunts wrote:

Thanks... Yeah, that's the only thing I can guess.
It got dark and the mosquitos were biting bad, halting my efforts to find a B2 sensor. I wasn't ambitious enough to pull off the undercariage plastic to look up from the bottom.
-marc
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Any dtc's? Check the tps at idle. I've seen some of these cause some wierd idle concerns. Also check the EGR for being partially open.
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No DTC's...
TPS was sitting at 0% at idle...
Real good call about the EGR - the car did throw a EGR code over the winter. It stated something that led me to believe it was sticking, I just don't remember the number or what it translated to. The car was running fine, and I figured I'd "get around to it", when it happened again. I can't believe I forgot about this...
Would a sticking EGR cause the 02 to respond strangely?
Everything I've heard and have been able to dig up, point to these motors only having one (pre-cat) 02 sensor.
Thanks, -marc
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A stuck open EGR effectively dumps more air into the engine, causing a lean mixture.
On checking the tps, pay more attention to the voltage than the percentage. The computer will automatically set 0% to whatever the tps voltage when the car is started. So, if the tps is reading erroneously high at idle, say 1.30 Volts or so, then the computer will set 0% equal to 1.30 Volts.
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Wouldn't you advise he does a TPS sweep:
With an analog VOM, and check for flat spots?
Respectfully submitted,
Refinish King

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Sweeping the tps can't hurt, but the only thing that will affect idle is its reading with the throttle closed.
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True!
Thank you,
Refinish King

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