new O2 but lower mileage? - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 09-20-2004, 08:53 PM   #1
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Default new O2 but lower mileage?

just put on my new delco O2 over the weekend. drove 2 1/2 hours to get to ames and now finding my mileage is actually suffering. went from 30+ on the interstate to 20-24. does this have anything to do with the O2 (no codes have been set), or should it be attributed to the fact that my car has been surging pretty badly and the TC probably isn't locked up as much as its supposed to be?
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Old 09-21-2004, 02:59 PM   #2
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any ideas? am i being too vague?
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Old 09-21-2004, 03:00 PM   #3
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I'd put my money on the TC. A new O2 wouldn't do that unless it was faulty. But since there are no codes, then I'm sure it'* fine.
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Old 09-21-2004, 07:50 PM   #4
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I am having the same problem, replaced my O2 with a delco sensor, and seems I am getting lower mpg. Waiting for tis tank to run out so I can figure out how much. Replaced in hopes of improving it, might throw the old one in if it is a lot lower.
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Old 09-21-2004, 08:26 PM   #5
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I've seen a few people who go from the bosch to the ac delco and lose fuel economy. However, you need to make sure you compare equal driving [IE if you drive primarly on highways, drive there, not in the city, or vise versa]. Hopefully it'll level out.


-justin
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Old 09-22-2004, 01:29 AM   #6
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If the TC is locked up and the car is in over drive at about 75 mph it should be around 2200 rpms, but if its shuddering and unlocking as in going back into 3rd gear, the rmps will jump up around 3200 and your mileage will suffer ALOT.
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Old 09-22-2004, 09:38 AM   #7
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On mine it was delco to delco, I think it was the stock sensor, have under 70k on the car. I mainly use the car to work and back, and thats what I have been basing mpg on. Is there a "burn in" time for an O2?
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Old 09-22-2004, 04:36 PM   #8
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What about an NTK sensor from NGK? Anyone know anything about these as far as working goes? Got one a couple of weeks ago but havent installed it yet. Im guessing the one in there is super old and has probably never been replaced but I dont know.
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Old 09-22-2004, 07:38 PM   #9
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i've never heard of any kind of "burn in time." from what i know a pcm wouldn't need to learn a new sensor. i even reset the computer after the install. its a delco to another delco, so that shouldn't be the issue. also seem a little low on power. it doesn't downshift and push me back in the seat the way it did a few days ago. ideas?
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Old 09-23-2004, 04:20 AM   #10
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Quote:
Originally Posted by CmptrNerd
What about an NTK sensor from NGK? Anyone know anything about these as far as working goes? Got one a couple of weeks ago but havent installed it yet. Im guessing the one in there is super old and has probably never been replaced but I dont know.
I have and I think it might relate a little to the 'problem' some so I'll rant for a sec :P

I used one for a while. Half of the time it was in the manifold my engine was torn apart though. When I first hooked up Wills scantool it looked like the readings were fine, other than at idle. It reacted quickly but would bounce around a lot, seemed really hyperactive. It only had about 3k miles or so on it. The bad part about being hyperactive is as it jumped wildly it would bounce on like 430mv then up to 700 then 680 then 550. This would make the car run rich for a little bit because the PCM only listens to 400-600mv, so I've read. So at 430mv it richens it up a little and doesn't 'hear' back from it till it reads 550. If the real reading should be been 550 I was running rich for a little bit and didn't need to be.

I replaced it with a Borg Warner a few weeks ago and rechecked the o2 readings. This time the highs were higher and the lows were lower. It was much smoother in its readings and wouldn't jump all over the place as much. It would still read a tad random at times but less than 1/4 of the time the NGK did. This, obviously, would help the engine only use as much fuel as it needs.


I didn't keep good track of the mpg but with this but I think differences in manufacturing quality may account for a bit of gas mileage. Aparently you really have to watch out. When I got the Borg Warner the first one they handed me, still "fresh" in the box, was really nasty looking. Almost looked used. They took the next on off the shelf and it looked MUCH better. Makes me wonder how nasty the element is on some of these.

I type too much huh
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