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O2 sensor placement

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Old May 23, 2007 | 12:38 PM
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Default O2 sensor placement

I just installed new head gaskets and pacesetter LTs and I havent extended the wires for the two front O2s yet...... my rears have been deleted. what happens if u have the two front O2s plugged in, but not threaded in the header hole??? i wanna start it up and get it idleing.......................
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Old May 23, 2007 | 12:44 PM
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It won't idle about 30 seconds after the car hits closed loop (when coolant temp becomes greater than ~100*F). The O2 sensors will read the oxygen content in the air outside of the exhaust and the PCM will start dumping in all kinds of fuel as this will appear as a severly lean condition. You need to have the front O2's in the exhaust stream sealed up tight unless the car is programed to run in open loop full time.
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Old May 23, 2007 | 01:33 PM
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ok thank you for the quick reply......... i am running the car open headers.... real open headers, no y pipe i will get those extended and in their holes, and then get it over to the tuner to be retuned and get it to idle. it wont idle at all anyways, weather its cold or up to temp
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Old May 23, 2007 | 02:26 PM
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Well, you're going to run into the same issue with open headers. The exhaust needs to be sealed anywhere near the O2's if you're going to run closed loop. If you run open loop, then you can run open headers all day long and don't even need the O2's.
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Old May 23, 2007 | 04:27 PM
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can u explain why someone would run in open loop instead of closed loop??
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Old May 23, 2007 | 04:55 PM
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open loop is default for the the ecu. aka produced the most emissions, it uses default settings until the ecu can run all diagn and current conditions are met aka a/f ratio water temp, if u have it tuned in open loop u can control the defaults and hence ridding yourself of o2s ect. however you will never be near as fuel efficient in open loop.
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Old May 23, 2007 | 09:52 PM
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ok......... anyone else???
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Old May 23, 2007 | 10:36 PM
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Originally Posted by ricethis
can u explain why someone would run in open loop instead of closed loop??
This allows the car to be set (like a carb'd car) and not have outside (aka PCM) interference. Sometimes, the NBO2's create more problems than good - mostly on cars with long tube headers that have moved them further downstream to a cooler location. Cam'd cars with a good deal of overlap only add to the problem since they introduce more fresh, unburnt oxygen into the exhaust stream. Running open loop eliminates the need for O2 sensors in the eyes of the PCM. I have been in open loop since I bought the car pretty much. In fact, that's how the shop who did the install tuned the car...although they did a shitty job IMO. The point is, you should take note to the fact that I'm talking "in the eyes of the PCM." The down side is, day to day you may not be seeing the same AFR as changes in weather and what not can alter your AFR. That's why I don't go anywhere without my WBO2. That way, I can keep an eye on things. But, that (the WB) doesn't affect the PCM. Make a little more sense?
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Old May 25, 2007 | 10:28 AM
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im not going to be driving the car daily, maybe just once or twice a week....... i hate o2s and wish i could just get rid of them....... so your saying that i can have my car tuned in open loop and be fine? my gas mileage cant get any worse so i dont care about that lol. im running it open headers, no Y pipe...... how do you monitor your car? do you have a tuning program??
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