Stock O2 sensor readings and configuration.
02-25-19, 05:13 AM
#1
Pole Position
Thread Starter
Stock O2 sensor readings and configuration.
I've tried explaining this problem to several people now and I will type it up here again in hopes of finding someone that has a decent answer. The stock is300 has 4 exhaust sensors. 2 upstream, 2 downstream. There are 3 total cats.
Bank 1 -> upstream sensor 1 -> cat 1 -> downstream sensor 1 -> cat 3 -> downstream sensor 2.
Bank 2 -> upstream sensor 2 -> cat 2 -> cat 3 -> downstream sensor 2.
This is stock. The "problem" is there is that downstream sensor 1 in between two cats, or there is one downstream sensor behind one cat and there is one downstream sensor behind 2 cats. This "is not normal" for what I've seen on other cars. I have modified my car but I have a CEL for o2 sensors out of range. My setup is as follows:
manifold -> turbo -> upstream sensor 1 & 2, wideband sensor, catalytic convertor, downstream sensor 1 & 2.
I **thought this would work but my suspicion is that the stock ecu is not happy because the downstream sensor one needs to read slighly richer than the downstream sensor 2.
Downstream sensor 1 is after 1 cat only while sensor 2 is behind 2 cats..... yet they are both "downstream sensors". My guess is that the stock ecu knows the difference in o2 sensor readings from these two sensors and knows that there is no cat between them anymore. Has anyone done testing on this or know for sure?
I'm interested both in how it is supposed to work and how to fix it in my turbo is300 so that the CEL goes away and it thinks the exhaust is stock. Any help is greatly appreciated.
Bank 1 -> upstream sensor 1 -> cat 1 -> downstream sensor 1 -> cat 3 -> downstream sensor 2.
Bank 2 -> upstream sensor 2 -> cat 2 -> cat 3 -> downstream sensor 2.
This is stock. The "problem" is there is that downstream sensor 1 in between two cats, or there is one downstream sensor behind one cat and there is one downstream sensor behind 2 cats. This "is not normal" for what I've seen on other cars. I have modified my car but I have a CEL for o2 sensors out of range. My setup is as follows:
manifold -> turbo -> upstream sensor 1 & 2, wideband sensor, catalytic convertor, downstream sensor 1 & 2.
I **thought this would work but my suspicion is that the stock ecu is not happy because the downstream sensor one needs to read slighly richer than the downstream sensor 2.
Downstream sensor 1 is after 1 cat only while sensor 2 is behind 2 cats..... yet they are both "downstream sensors". My guess is that the stock ecu knows the difference in o2 sensor readings from these two sensors and knows that there is no cat between them anymore. Has anyone done testing on this or know for sure?
I'm interested both in how it is supposed to work and how to fix it in my turbo is300 so that the CEL goes away and it thinks the exhaust is stock. Any help is greatly appreciated.
Last edited by daddystop; 02-27-19 at 04:39 AM.
02-27-19, 08:00 AM
#3
Driver School Candidate
I used the work as an OBD calibration engineer (not for Toyota). Each automaker develops their own strategy for how to diagnose each system, but there are generally a lot of similarities amongst them.
You are correct that the feedback from the O2 will be influenced by the catalyst. In fact, the ecu purposely dithers the AFR from rich to lean all the time so the upstream O2 sensors produce a trace that looks like a sinusoidal wave. The catalyst can temporarily store the excess oxygen in the exhaust during the lean swings, and then uses it to complete combustion during the rich swings. The catalysts work more efficiently when done this way.
The ecu can diagnose the performance of the catalyst(s) by comparing the rich/lean swings of the upstream O2 sensor to the signal trace from the downstream O2 sensor. If the catalysts are working properly, the downstream trace should essentially be a flat line...
However, usually the automakers that choose to use a "mid bed" O2 sensor positioned between catalysts are basing their fuel trims, in part, on the readings from the O2 sensor in the middle. I can't say this for sure with the Toyota... But that's how we did it where I was, and we were one of the few companies to have a mid bed O2.
Now, you can't properly diagnose the catalyst unless you have properly functioning O2 sensors! So there are a batch of monitors that look at the O2 sensor signal and infer from it whether or not the O2s are working correctly...
With that said, the "out of range" fault codes are OBD-1 codes, which means they are there to diagnose basic circuit functionality - NOT operational performance of the system. The ecu has been programmed to look for basic high and low limits - between which the sensor must always be.
I assume you are getting these fault codes while the Toyota ecu is hooked up and in control???
Which of your O2s are giving you the OOR fault codes?
You are correct that the feedback from the O2 will be influenced by the catalyst. In fact, the ecu purposely dithers the AFR from rich to lean all the time so the upstream O2 sensors produce a trace that looks like a sinusoidal wave. The catalyst can temporarily store the excess oxygen in the exhaust during the lean swings, and then uses it to complete combustion during the rich swings. The catalysts work more efficiently when done this way.
The ecu can diagnose the performance of the catalyst(s) by comparing the rich/lean swings of the upstream O2 sensor to the signal trace from the downstream O2 sensor. If the catalysts are working properly, the downstream trace should essentially be a flat line...
However, usually the automakers that choose to use a "mid bed" O2 sensor positioned between catalysts are basing their fuel trims, in part, on the readings from the O2 sensor in the middle. I can't say this for sure with the Toyota... But that's how we did it where I was, and we were one of the few companies to have a mid bed O2.
Now, you can't properly diagnose the catalyst unless you have properly functioning O2 sensors! So there are a batch of monitors that look at the O2 sensor signal and infer from it whether or not the O2s are working correctly...
With that said, the "out of range" fault codes are OBD-1 codes, which means they are there to diagnose basic circuit functionality - NOT operational performance of the system. The ecu has been programmed to look for basic high and low limits - between which the sensor must always be.
I assume you are getting these fault codes while the Toyota ecu is hooked up and in control???
Which of your O2s are giving you the OOR fault codes?
02-27-19, 08:09 AM
#4
Driver School Candidate
Also, I have timing curves for my turbo IS. Unfortunately it's not a 3D map because the ecu is an older-than-the-hills Haltech that provides 17 2D tables; one for zero rpm, and then another for 500, another for 1000, etc etc up to 8000rpm. I'd be happy to share. I have a VVTi engine with GTE rods/pistons. Unfortunately I'm not sure if it has a thicker head gasket or not. But, my setup was configured many, many years ago and it's never broken despite having changed hands several times (assuming each previous owner took their turn gang-raping it).
I'd be happy to share, but it'll take some doing. I can tell you this: At 1psi boost, the timing is about 20º and sinks to 15º by 8-9psi. It maintains 15º up to 25psi. The timing curves look almost identical for all the engine speeds.
It takes some heavy, heavy "pinging" to break a piston on a naturally aspirated engine. Not impossible, but I wouldn't exactly call that a "ping". It sounds more like an engine being started on Ether (starting fluid), if you've ever heard that. Heavy, horrible knocking that sounds like a little gremlin is hammering on your engine from the inside... A little ping ping isn't going to break pistons.
I'd be happy to share, but it'll take some doing. I can tell you this: At 1psi boost, the timing is about 20º and sinks to 15º by 8-9psi. It maintains 15º up to 25psi. The timing curves look almost identical for all the engine speeds.
It takes some heavy, heavy "pinging" to break a piston on a naturally aspirated engine. Not impossible, but I wouldn't exactly call that a "ping". It sounds more like an engine being started on Ether (starting fluid), if you've ever heard that. Heavy, horrible knocking that sounds like a little gremlin is hammering on your engine from the inside... A little ping ping isn't going to break pistons.
02-27-19, 02:59 PM
#5
Pole Position
Thread Starter
I **finally did a compression test the other day on my car. I broke it in June 2018 lol. The results were not good:
#1 - 150
#2 - 90
#3 - 180
#4 - 180
#5 - 110
#6 - 120
Thank you very much Hodgdon for your reply. It sounds to me like my thinking wasn't far off from what is actually done in the R&D and Production side of the industry. I'd love to see a screenshot of your timing. One thing I was curious about is how do you map the VVTI? I have no idea how that is supposed to be set up, and I hope it's obvious that I'm not necessarily interested in paying someone else to tune my car.
The way wiring goes in the IS300 is:
Stock ECU is connected to:
* stock o2 sensors
* stock throttle body
* stock air flow meter
* stock auto trans
ProEFI 128 is connected to:
* ignition
* fuel
* wideband o2 sensor
* map/iat
* etc
The only purpose of the stock ecu is to control the A650E transmission and the other creature comforts the car came with. Because of the o2 sensor problem the stock ecu is having it has put the "trac" light on flashing slowly. This means that I have no traction control. The trans isn't in full limp mode but the traction control doesn't work. The shift up/down from the steering wheel still works as does all the manual gear selecting on the floor shifter. I wanted to keep the auto trans and paid IPT to upgrade one for me. It's very nice except the weak 3rd gear sprague which is kind of a buzz kill not being able to do full torque shifts between 2nd and 3rd gear.
In ANY case. I really appreciate you taking the time to reply. I've had a challenging time finding anyone in the Lexus community that was knowledgeable enough and willing to help. What do you think could cause an otherwise healthy engine to end up with those compression numbers and filling the intake pipe w/ oil? I would think if there was excessive blowby in the crank case that it could cause a very large amount of air to go through the PCV system and maybe slurp a lot of oil out of the VC that way..... I dunno how farfetched that theory is/sounds.
#1 - 150
#2 - 90
#3 - 180
#4 - 180
#5 - 110
#6 - 120
Thank you very much Hodgdon for your reply. It sounds to me like my thinking wasn't far off from what is actually done in the R&D and Production side of the industry. I'd love to see a screenshot of your timing. One thing I was curious about is how do you map the VVTI? I have no idea how that is supposed to be set up, and I hope it's obvious that I'm not necessarily interested in paying someone else to tune my car.
The way wiring goes in the IS300 is:
Stock ECU is connected to:
* stock o2 sensors
* stock throttle body
* stock air flow meter
* stock auto trans
ProEFI 128 is connected to:
* ignition
* fuel
* wideband o2 sensor
* map/iat
* etc
The only purpose of the stock ecu is to control the A650E transmission and the other creature comforts the car came with. Because of the o2 sensor problem the stock ecu is having it has put the "trac" light on flashing slowly. This means that I have no traction control. The trans isn't in full limp mode but the traction control doesn't work. The shift up/down from the steering wheel still works as does all the manual gear selecting on the floor shifter. I wanted to keep the auto trans and paid IPT to upgrade one for me. It's very nice except the weak 3rd gear sprague which is kind of a buzz kill not being able to do full torque shifts between 2nd and 3rd gear.
In ANY case. I really appreciate you taking the time to reply. I've had a challenging time finding anyone in the Lexus community that was knowledgeable enough and willing to help. What do you think could cause an otherwise healthy engine to end up with those compression numbers and filling the intake pipe w/ oil? I would think if there was excessive blowby in the crank case that it could cause a very large amount of air to go through the PCV system and maybe slurp a lot of oil out of the VC that way..... I dunno how farfetched that theory is/sounds.
02-27-19, 03:47 PM
#6
Driver School Candidate
I suspect you do not have tight enough control of the AF mixture to satisfy the Toyota ecu. It is looking for a rich/lean/rich/lean dither, from ~14.2-15.0 (lambda .95-1.05) with a frequency of about 1 second. That's how catalysts work best.
You might try giving fuel/spark control back to the Toyota ecu, to see if the codes go away. Else, I still think it possible you have a basic circuit problem; either the sensors themselves are unhappy, or the wiring from them to the ECU... You can test this by giving fuel control to the Toyota ecu. Obviously, do not get into boost when you do this!
My turbo arrangement has a Haltech E6K (yes, from like 15 years ago) piggyback'd. It has control of fuel and spark ONLY. The Toyota ecu maintains control of the throttle, VVTi, instrument cluster, etc etc. There are programmable ECUs that can do the throttle and vvti, but I see little benefit. I think you should allow the Toyota ecu to control your VVTi.
I'll work on posting screen shots of my timing tables.
Regarding your broken engine... Yikes. I tested my compression only a few weeks ago and got 165-175 across the board. All of yours seen low. How yours broke, I've no idea. Perhaps your turbo wastegate wasnt enough to prevent any/all boost - and you inadvertantly blee boost into the engine? I don't believe running a stock 2JZ-GE VVTi on 87 octane would break it, but I've been wrong before (once).
You might try giving fuel/spark control back to the Toyota ecu, to see if the codes go away. Else, I still think it possible you have a basic circuit problem; either the sensors themselves are unhappy, or the wiring from them to the ECU... You can test this by giving fuel control to the Toyota ecu. Obviously, do not get into boost when you do this!
My turbo arrangement has a Haltech E6K (yes, from like 15 years ago) piggyback'd. It has control of fuel and spark ONLY. The Toyota ecu maintains control of the throttle, VVTi, instrument cluster, etc etc. There are programmable ECUs that can do the throttle and vvti, but I see little benefit. I think you should allow the Toyota ecu to control your VVTi.
I'll work on posting screen shots of my timing tables.
Regarding your broken engine... Yikes. I tested my compression only a few weeks ago and got 165-175 across the board. All of yours seen low. How yours broke, I've no idea. Perhaps your turbo wastegate wasnt enough to prevent any/all boost - and you inadvertantly blee boost into the engine? I don't believe running a stock 2JZ-GE VVTi on 87 octane would break it, but I've been wrong before (once).
02-28-19, 07:28 AM
#7
Pole Position
Thread Starter
I cannot give fuel control back to the stock ecu without installing the stock injectors again.... and there's no point in doing it on the low compression motor. You may be right about the WG not being able to prevent all boost. The car was loaded pretty well with weight and we were going up and down hills. What do you think the "fastest/best" way to get this car back on the road is?
1. Pull engine and remove pistons, inspect block for damage, install new pistons on used GTE rods and reassemble.
2. Buy ebay engine, disassemble, install new pistons on used GTE rods reassemble, swap engines/accessories into running car.
3. buy ebay engine, swap engine/accessories into running car, disassemble low compression engine, install new pistons on used GTE rods, shelve for later day.
1. Pull engine and remove pistons, inspect block for damage, install new pistons on used GTE rods and reassemble.
2. Buy ebay engine, disassemble, install new pistons on used GTE rods reassemble, swap engines/accessories into running car.
3. buy ebay engine, swap engine/accessories into running car, disassemble low compression engine, install new pistons on used GTE rods, shelve for later day.
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02-28-19, 08:06 AM
#8
Driver School Candidate
You should do option 1, but you should should inspect the block FIRST using an endoscope. You can buy them for under $20 and it's a great tool to have. With piston at BDC, look for scoring and/or scuffing on the cylinder walls.
If they look good, pull the engine, give it a quickie touch hone with a dingleberry, swap in some GTE rods/pistons with fresh rings and reassemble/reinstall.
If the cylinders are hurt, buy a good miles GE VVTi and do same as above.
If they look good, pull the engine, give it a quickie touch hone with a dingleberry, swap in some GTE rods/pistons with fresh rings and reassemble/reinstall.
If the cylinders are hurt, buy a good miles GE VVTi and do same as above.
03-20-19, 06:51 AM
#10
Pole Position
Thread Starter
So I've had some time to ponder and do some car work (although it was on my 1991 Eagle Talon and not the IS300)..... I've considered that there may not be anything "catastrophically" wrong w/ my motor.
It was suggested to me last night by a friend that has been helping me ever since the damn thing puked oil into the intake that "it's possible it's just the headgasket". This seems VERY plausible to me now that I think about it.... and may allow me to get the car back on the road quickly.
The headgasket can blow between the cylinder and an oil drain in the head. My #2 cylinder is the one that has the worst compression. The high blow by in the intake pipe could be because compression was leaking into the crank case through a blown hg. I don't know why I didn't think of this before. I'm going to work to remove the head from the car now I think. I was going to scope the bore but I decided it was a lot of messing around when I knew something was bad anyway. I'm just glad that it's not a engine removal job (yet). I will keep you all updated as I make progress..... maybe one day I'll post some pictures here too.
It was suggested to me last night by a friend that has been helping me ever since the damn thing puked oil into the intake that "it's possible it's just the headgasket". This seems VERY plausible to me now that I think about it.... and may allow me to get the car back on the road quickly.
The headgasket can blow between the cylinder and an oil drain in the head. My #2 cylinder is the one that has the worst compression. The high blow by in the intake pipe could be because compression was leaking into the crank case through a blown hg. I don't know why I didn't think of this before. I'm going to work to remove the head from the car now I think. I was going to scope the bore but I decided it was a lot of messing around when I knew something was bad anyway. I'm just glad that it's not a engine removal job (yet). I will keep you all updated as I make progress..... maybe one day I'll post some pictures here too.
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