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Post by 91clipseDOHC on Jun 16, 2016 19:35:53 GMT -5
Yes on the sensors. Yea ethanol, from a fuel standpoint, isn't bad but the engine needs to be tuned for it, however it's not very practical. Some aftermarket setups have a switch in the glove box to change the mapping and some have a controller that can switch between a few different blends. These trucks inparticular were not designed to run on e85 or anything above 10% ethanol. I have tried the ethanol free stuff and it loved it. Right, on my Evo I had dual maps, one tune for E85 and one for 91 octane. To switch between the two I would turn the key "on", hold the gas pedal for a few seconds until the check engine light would flash indicating I had switched maps, and then I would start it up. It was that simple. However that was on a turbocharged performance car that I raced. I have no interest in running E85 on my Montero Sport and I apologize for getting off topic
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Post by jkdv8 on Jun 19, 2016 17:33:27 GMT -5
Yes on the sensors. Yea ethanol, from a fuel standpoint, isn't bad but the engine needs to be tuned for it, however it's not very practical. Some aftermarket setups have a switch in the glove box to change the mapping and some have a controller that can switch between a few different blends. These trucks inparticular were not designed to run on e85 or anything above 10% ethanol. I have tried the ethanol free stuff and it loved it. Right, on my Evo I had dual maps, one tune for E85 and one for 91 octane. To switch between the two I would turn the key "on", hold the gas pedal for a few seconds until the check engine light would flash indicating I had switched maps, and then I would start it up. It was that simple. However that was on a turbocharged performance car that I raced. I have no interest in running E85 on my Montero Sport and I apologize for getting off topic Well that makes things easier.
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Post by ES_97Sport on Jun 20, 2016 13:21:35 GMT -5
The ethanol bit makes sense but the levels at the pump around me haven't changed in the time I've had mine. When I first got it I could get upwards of 25mpg on road trips and it slowly decreased from there which is typical as a car ages. I have not taken it on a road trip recently to compare but the last time, a few years back, it was around 21. The issue is the pumps say 10% - in reality it can be anywhere from none to 15-20% ethanol on the outside. There is an allowed variance for the manufacturers. Its impossible for the mix to be exactly 10% all the time so that was built in when the regulations were put in place years ago. I don't remember who it was now, but they busted a refiner here in CO some years ago shipping 15-16% out to the stations for pumps labeled 10% max. Edward
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Post by ES_97Sport on Jun 20, 2016 13:31:05 GMT -5
As I recall only the front o2 sensor effects the fuel trims and the rear is just there to verify that the converter is working, correct? .... No. Both pre and post-CAT O2 sensors are used for fuel management. It is heavily weighted to the pre-CAT O2 sensors, but the rear's are still used. I don't know where the idea that the rear's aren't used came from because the FSMs say differently and my testing confirms it. Edward
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Post by jkdv8 on Jun 21, 2016 15:16:34 GMT -5
The issue is the pumps say 10% - in reality it can be anywhere from none to 15-20% ethanol on the outside. There is an allowed variance for the manufacturers. Its impossible for the mix to be exactly 10% all the time so that was built in when the regulations were put in place years ago. I don't remember who it was now, but they busted a refiner here in CO some years ago shipping 15-16% out to the stations for pumps labeled 10% max. Edward Yea, that wouldn't surprise me. That would explain the few times I attributed rough running on bad gas when it's possible it actually was. I think even the owners manual states not to run anything over 10% ethanol through it.
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Post by jkdv8 on Jun 21, 2016 19:37:02 GMT -5
As I recall only the front o2 sensor effects the fuel trims and the rear is just there to verify that the converter is working, correct? .... No. Both pre and post-CAT O2 sensors are used for fuel management. It is heavily weighted to the pre-CAT O2 sensors, but the rear's are still used. I don't know where the idea that the rear's aren't used came from because the FSMs say differently and my testing confirms it. Edward I think some manufacturers use this type of fuel control although, from what I've seen with these trucks leads me to believe they do not. I was curious myself though so I looked at the manual I have. In the fuel injection section, it states that it uses the theoretical ideal air/fuel mixture (stoichiometric/lambda 1) in closed loop control to maintain peak efficiency of the catalyst. It doesn't say though if its both fronts or all four, just that it uses the sensors. Peak efficiency however occurs at different points on either side of the stoichiometric point. Two of the gases are converted on the leaner side while the other on the richer side. The act of the computer bouncing back and forth (based on feedback from sensor 1) while keeping as close to lambda 1 (for peak power and fuel economy) keeps the converter at peak performance so in essence all the rear one does is monitor that it is occurring. Also, the computer uses the front O2 to keep enough oxygen in the exhaust to allow the burning off of hydrocarbons. If the computer was taking readings from the rear O2 to determine fuel ratios for catalyst efficiency or whatever it would need to have some input reference but they essentially maintain a consistent reading. When they start to erratically bounce around like the front ones do it is indication that the catalyst has failed, in most cases. I've also never heard of a drivability issue from any vehicle with a failed cat and that would be the best time if any for the computer to try to control the ratio to help keep peak catalyst efficiency.
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Post by ES_97Sport on Jun 22, 2016 14:42:29 GMT -5
... I've also never heard of a drivability issue from any vehicle with a failed cat and that would be the best time if any for the computer to try to control the ratio to help keep peak catalyst efficiency. The information I found was in the Gen 1 FSMs. The testing was by monitoring ST and LT fuel trims through several different CATs and O2 sensors in various states over a couple years time. What I know happens because I've repeated this half a dozen times, is that with a new forward O2 and new CAT, a bad rear O2 results in a - dip in fuel mileage, driveability and a change in LTFT (which echos the dip in mileage). For whatever reason, whether the ECM/PCM DOES actively uses the rear sensor(s) or not, the effect is the same. Edward
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Post by dirk on Jun 22, 2016 23:45:00 GMT -5
I suggest new O2 sensors about as often as we need new iridium plugs. I think every 80 to 100K or 10 years. I know they are not lifetime parts, and every vehicle I've changed one bad one in the others usually go bad relatively soon after. And I've always kept my cars a long time, my Saturn I just gave my daughter has 325K miles on it. After new O2 sensors the milage always went back up and the difference has paid for the 02 sensors and more.
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Post by ES_97Sport on Jun 23, 2016 14:30:07 GMT -5
I suggest new O2 sensors about as often as we need new iridium plugs. I think every 80 to 100K or 10 years. I know they are not lifetime parts, and every vehicle I've changed one bad one in the others usually go bad relatively soon after. And I've always kept my cars a long time, my Saturn I just gave my daughter has 325K miles on it. After new O2 sensors the milage always went back up and the difference has paid for the 02 sensors and more. Yep. When i started going through the manufacturer's recommendations for O2 sensors several years ago, they all said between 80k and 160K. That was for the OEM stuff, not aftermarket. Yea, they are definitely not 'lifetime' parts. I would figure with the experience I've had with OEM O2 sensors, about every 120K, but that doesn't actually work. As the engine gets older and starts burning oil, the lifespan of the O2 sensors goes down. So, really after the first 120-160K it probably depends on how tight the engine is. If its burning full synthetic oil, that's supposed to be even worse for O2 sensors. Edward
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Post by jkdv8 on Jun 23, 2016 16:24:35 GMT -5
What I know happens because I've repeated this half a dozen times, is that with a new forward O2 and new CAT, a bad rear O2 results in a - dip in fuel mileage, driveability and a change in LTFT (which echos the dip in mileage). Edward The computer does however ignore the sensor readings in open loop and there is a very slim chance that it ever went into closed loop with a faulty sensor. On all cars that I know of the computer won't go into closed loop if it detects a failed or inconsistent O2 whether it's front or rear and throws the check engine light. I'm not even sure if it would go into closed loop if the SES light is on and even more so for anything that the computer uses (i.e. coolant sensor etc.) to determine whether or not it goes into closed loop. Some cars do use both sensors to cross reference each other (for sensor performance and cat performance) so without the rear it might err on the side of caution in case the front isn't behaving. If it can't be certain that the engine isn't running too lean (increased risk of detonation and increases heat) for extended period of time it would default to the rich fuel map. Limp mode safety feature so to speak to keep from grenading the engine.
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