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So, I'll start this question off simply and explain my situation in the process. I have a Magnum tuning O2 simulator that I was going to use to temporarily fix my bad gas mileage by tricking the O2, I don't have a catalytic converter so it makes it run really rich. At the moment it has an EML light and a code for p1498 which is essentially a vacuum leak somewhere. I'm getting to the bottom of that but in the meantime I wanted to know if hooking up my O2 simulator will be effective with the EML light on(The EML light may be because of something to do with the plastic intake duct so I just haven't had the resources or time to look, for now I'm just checking vacuum lines)
The rear O2 only verifies that the catalytic converter is working. The front O2 is the one that provides info to the ECM about fueling. I would not recommend trying to fool the front O2 as that could be detrimental to your engine.
To quote Independence Day, that's not entirely accurate.
The rear O2 is used to monitor converter function, yes, but it is also used before the converter lights off to crosscheck the rear and front O2s against each other to see if the front has skewed. They assume the front skews and not the rear because the front sees a lot more heat, so it should degrade faster.
The rear O2 is also used for fuel trim to a degree, because the whole point of closed loop operation is to keep the converter happy. So even if the front O2 is happy but the rear isn't .68-.7v like should be seen with a working cat, the computer will trim a little as necessary.
To quote Independence Day, that's not entirely accurate.
The rear O2 is used to monitor converter function, yes, but it is also used before the converter lights off to crosscheck the rear and front O2s against each other to see if the front has skewed. They assume the front skews and not the rear because the front sees a lot more heat, so it should degrade faster.
The rear O2 is also used for fuel trim to a degree, because the whole point of closed loop operation is to keep the converter happy. So even if the front O2 is happy but the rear isn't .68-.7v like should be seen with a working cat, the computer will trim a little as necessary.
I thought this logic was only used in cars with factory widebands? Since the narrowband O2 is very accurate in a small range and the wideband is less accurate over a much wider range, they impart some of the accuracy of the narrowband into the wideband. Ford calls it Fore-Aft Oxygen Storage control (FAOSC), I used to know the BMW acronym but I forgot it.
I have seen issues with fuel trims on an e39 with a rotted out downstream sensor though, so my own experience supports your assertion. Though I wonder what the purpose is as the upstream and downstream sensors are identical, they have the same uncertainty.
I thought this logic was only used in cars with factory widebands? Since the narrowband O2 is very accurate in a small range and the wideband is less accurate over a much wider range, they impart some of the accuracy of the narrowband into the wideband. Ford calls it Fore-Aft Oxygen Storage control (FAOSC), I used to know the BMW acronym but I forgot it.
I have seen issues with fuel trims on an e39 with a rotted out downstream sensor though, so my own experience supports your assertion. Though I wonder what the purpose is as the upstream and downstream sensors are identical, they have the same uncertainty.
It is used a lot in vehicles with widebands, but I think this is also just a side effect of widebands being more prevalent at the same time computer processing power has increased to allow this level of monitoring and trimming. There are plenty of computers that use this strategy with narrow band upstream sensors.
I am pretty sure Subaru is an outlier, they seem to ignore the downstream. When the (wide band) upstream starts to fail and the computer sends fuel trims so incredibly rich that it misfires... it sets a lean code because the fuel trims are so high. Nevermind that the downstream is pegged rich... real great error checking strategy you got there, guys.
i also thought downstream sensor is just for cat function check. trims and closed loop is a function of the upstream sensor readings. is that wrong!?
Essentially O2 sensors are not perfect, manufacturers can use the downstream O2 sensor in conjunction with the stock cat to measure how far off from perfect the upstream sensor is. My assumption was that this was only used for wideband-narrowband systems not narrowband-narrowband systems as the wideband is less precise than a narrowband.
When you put a non-fouler or a non-stock cat on the car you can throw off this calculation and you'll see it in your fuel trims. The best solution is to have a tune to disable this function, idk if that's even possible on this platform I haven't looked into it. On my Mustang I made my main driving tune have FAOSC disabled which eliminates this problem entirely, and then an "emissions" tune with it back on so I could pass testing. That car required FAOSC to be enabled or else the cat monitor would never finish, no guarantees that its the same here.
FAOSC has a limited effect on fueling through, it is only allowed to push the fuel trims a certain amount. Which is why you can get away with a non-fouler and no tune, its not enough error to really notice. Its wrong through, so if you wanted to do it "right" you need to keep the stock cat or disable the logic somehow.
Yeah, I am working on fixing it but I'm not sure what exactly is leaking since I just did a supercharger service
I’d bet a lot of money is the green gasket at the supercharger inlet tube. That’s what it was for me and seems to cause issues for a lot of other people too
I’d bet a lot of money is the green gasket at the supercharger inlet tube. That’s what it was for me and seems to cause issues for a lot of other people too
did you have to replace it? wondering if a smoke test would work to troubleshoot that
did you have to replace it? wondering if a smoke test would work to troubleshoot that
A smoke test will find it, mine was because I didn't properly seat the bypass tube and it misaligned the green gasket. I didn't try and re-use the old one I just replaced it.
I’d bet a lot of money is the green gasket at the supercharger inlet tube. That’s what it was for me and seems to cause issues for a lot of other people too
I figured out that the eml was being thrown because of the way the charge pipe was sitting due to a couple things, the first thing being that I have a 760i throttlebody and had to "modify" the bracket for it to sit right, and also since the kit came with a bpv hose that was too thick it made the charge pipe sit weird. It still has a p1498 but now it doesn't get an eml. I have only seen an eml a couple times since and cannot find a pattern between those incidents so I'll keep an eye on it.
I figured out that the eml was being thrown because of the way the charge pipe was sitting due to a couple things, the first thing being that I have a 760i throttlebody and had to "modify" the bracket for it to sit right, and also since the kit came with a bpv hose that was too thick it made the charge pipe sit weird. It still has a p1498 but now it doesn't get an eml. I have only seen an eml a couple times since and cannot find a pattern between those incidents so I'll keep an eye on it.
NOW you mention that you have a different throttle body. Did you have the computer retuned for it?
Throttle position is used for fuel calculations and fuel calculation error checking, if the throttle area per TPS is different, that's going to be seen as an error unless the computer has been recalibrated.
