O2 sensor on 5vzfe with dual exhaust
12-01-2020, 09:13 PM
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O2 sensor on 5vzfe with dual exhaust
Hello all, I am very excited about my first post on yota. I have been reading up on the posts here for months but decided it was time I signed up and started posting 
I have a 5vz-fe swapped 1983 Fj40 (which is a work in progress) so thought this would be relevant under the 4Runner and Tacoma section. I am based in Pakistan, so the engine is JDM with a JDM ECU (unreadable part number) but looks to be an early model ECU with the blocky connectors. The ECU does not support OBDII (or maybe it does and I haven't been able to figure it out. This is a side discussion that I need to have) so the troubleshooting is in the blind
Anyway, the PO installed a dual exhaust on the vehicle and the "pre-cat" O2 sensor is located on the bank 1 side exhaust pipe but I have looked at stock 5vzfe exhausts and the exhaust pipes from the two sides join in a Y right before the O2 sensor so the O2 is reading the exhaust from both engine sides. This leads me to believe that the O2 configuration on my FJ40 is wrong as it only reads when cylinder 1-3-5 fire but misses 2-4-6 and therefore reads 'lean' when the bank-2 side fires.
Is my understanding here correct or am I missing something? What should be done to fix this? Can I run two O2 sensor on both side and connect them in parallel circuit? The fuel consumption is terrible and the engine is always running rich (what I can tell from the strong smell of gas coming from the exhaust)
Please do share any comments/suggestions. Thanks in advance.
I have a 5vz-fe swapped 1983 Fj40 (which is a work in progress) so thought this would be relevant under the 4Runner and Tacoma section. I am based in Pakistan, so the engine is JDM with a JDM ECU (unreadable part number) but looks to be an early model ECU with the blocky connectors. The ECU does not support OBDII (or maybe it does and I haven't been able to figure it out. This is a side discussion that I need to have) so the troubleshooting is in the blind
Anyway, the PO installed a dual exhaust on the vehicle and the "pre-cat" O2 sensor is located on the bank 1 side exhaust pipe but I have looked at stock 5vzfe exhausts and the exhaust pipes from the two sides join in a Y right before the O2 sensor so the O2 is reading the exhaust from both engine sides. This leads me to believe that the O2 configuration on my FJ40 is wrong as it only reads when cylinder 1-3-5 fire but misses 2-4-6 and therefore reads 'lean' when the bank-2 side fires.
Is my understanding here correct or am I missing something? What should be done to fix this? Can I run two O2 sensor on both side and connect them in parallel circuit? The fuel consumption is terrible and the engine is always running rich (what I can tell from the strong smell of gas coming from the exhaust)
Please do share any comments/suggestions. Thanks in advance.
02-18-2023, 07:17 AM
#2
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Well I know this is an old thread but nobody responded to it and I've been lurking here for a bit so I decided to join. I personally think that redoing the exhaust so it merges into one pipe may be your best bet. You may be able to put an X pipe or an H pipe into the system and relocate the O2 sensor in the middle of X or H pipe but the problem after that is catalytic converter(s) I don't know if it could be done but I wonder if you could run 2 catalytic converters and then install another X/H pipe with the post catalytic converter sensor in the middle. There is another idea I have but it's definitely not legal in the United States so I don't want to post it lol
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