Fact or fiction: power loss from bad o2?
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From: Northwest AR
Fact or fiction: power loss from bad o2? I've heard several stories of cars running poorly and the end result being to replace o2 sensors. But I can't make sense of it if the sensors are not supposed to be referenced during WOT.
Is it really possible? And more so is it possible if no codes are being thrown and the sensors look to be cycling fine?
Is it really possible? And more so is it possible if no codes are being thrown and the sensors look to be cycling fine?
Teching In
Joined: May 2009
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From: Yucaipa, CA
Yep, I'm equally curious... I remember some heresay that the front O2 sensors impact the HP/fuel consumption but I've never heard a definite (or if the rear have an impact)
Anybody that has real knowledge on this please fill us in (I really would like to know because I have one bad front and back right now, lol)
Anybody that has real knowledge on this please fill us in (I really would like to know because I have one bad front and back right now, lol)
Thread Starter
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From: Northwest AR
Haha, I have about 30-40hp that likes to show up once in a blue moon (seriously no more than 5times since the car was put together last year)
I can't find anything wrong for the life of me and no one else has given me any other ideas. A friend said his race car was losing over .5 sec in the 1/8th and it turned out to be a faulty o2 sensor.
I'm becoming impatient with the car. I am quite sick of running with bolt on exhaust ls1 cars in a cammed car, especially knowing the power is there somewhere...its just hiding and rarely shows its face.
I can't find anything wrong for the life of me and no one else has given me any other ideas. A friend said his race car was losing over .5 sec in the 1/8th and it turned out to be a faulty o2 sensor.
I'm becoming impatient with the car. I am quite sick of running with bolt on exhaust ls1 cars in a cammed car, especially knowing the power is there somewhere...its just hiding and rarely shows its face.
Bad front o2's can absolutely affect performance, even WOT. For example, say you're cruising along and mash the throttle. If your fuel trims are 5% positive (lean) in the cell that you're in at the moment of mashing the throttle, then 5% extra fuel gets added onto your commanded WOT a/f ratio. The factory tune is pig rich to begin with, any excess fuel being dumped from lean fuel trims will make it even worse.
Teching In
Joined: May 2009
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From: Yucaipa, CA
That's crazy - yep, it makes sense on the lean/air to fuel ratio impact....Kinda of a newbie question but this is my first LS1 (and I've already had the difficulty of changing spark plugs) How hard is it to replace your O2's (front and back) without a lift or stands? Also, anyone know where to get them as cheap as possible???
Thank you!
Thank you!
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Thread Starter
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From: Northwest AR
mine are fluctuating and my trims seem to be in order so I dunno if that could be my problem...i'm just running out of ideas
the car runs WOT and shifts like ****, short shifts first gear and is too loose going into 3rd...fuel mileage seems fine though
the car runs WOT and shifts like ****, short shifts first gear and is too loose going into 3rd...fuel mileage seems fine though
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I have the exact same problem but the previous owner cut the cats out without a retune so I'm positive that's my problem.
Staging Lane
Joined: Jun 2009
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From: Southern California
usually, when you have a bad O2 sensor, it will throw a code and the car will just run off of "default" settings that are not as exact as when the O2 sensor is working, almost as if it is running in Open Loop, making it lose some power. So if it is not throwing any codes and it is cycling just fine, then i doubt thats the problem.
If you feel you're loosing power from the O2's, unplug the front set and zip tie the wires out of the way, and drive it. It will set a DTC but it will also default to open-loop mode. If the car feels like it has the power it usually doesn't, you probably have a bad O2 or a tune issue related to closed loop. I had my car tuned before to run strictly in open loop since the throttle response is much, much better.
Last edited by Arc00TA; Jul 8, 2009 at 01:29 PM.
Teching In
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From: Yucaipa, CA
Arc00TA
TECH Resident
My Garage
"If you feel you're loosing power from the O2's, unplug the front set and zip tie the wires out of the way, and drive it. It will set a DTC but it will also default to open-loop mode. If the car feels like it has the power it usually doesn't, you probably have a bad O2 or a tune issue related to closed loop..."
Thanks for the advice - I know for sure one of the front are bad...so driving without the o2's in place won't hurt the car in anyway? I don't have access to a lift or jack stands (apartment living, gotta love it) are the o2's easily accessible if I were to pull onto a curb or something?
TECH Resident
My Garage
"If you feel you're loosing power from the O2's, unplug the front set and zip tie the wires out of the way, and drive it. It will set a DTC but it will also default to open-loop mode. If the car feels like it has the power it usually doesn't, you probably have a bad O2 or a tune issue related to closed loop..."
Thanks for the advice - I know for sure one of the front are bad...so driving without the o2's in place won't hurt the car in anyway? I don't have access to a lift or jack stands (apartment living, gotta love it) are the o2's easily accessible if I were to pull onto a curb or something?
Joined: Nov 2003
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From: Wichita KS / Rancho San Diego
If you feel you're loosing power from the O2's, unplug the front set and zip tie the wires out of the way, and drive it. It will set a DTC but it will also default to open-loop mode. If the car feels like it has the power it usually doesn't, you probably have a bad O2 or a tune issue related to closed loop. I had my car tuned before to run strictly in open loop since the throttle response is much, much better.
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From: reykjavík, iceland
I somehow forgot to reconect my left front sensor before i started it few days ago, i just backed it out of the workshop before i noticed and conected it, the car felt like it had lost 30-40 hp's at least until i deleted the codes
Yeah I wasn't saying for optimum, but it can help to troubleshoot and see if you have a bad O2.