Are my O2s sleepy (image inside)?
01-01-2012, 10:10 PM
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Are my O2s sleepy (image inside)? While searching for the cause(s) of my problem(s), I ran across an image posted by jimmyblue showing "happy" versus "sleepy" O2s (though I am sure mine are "grumpy" or "dopey"). My O2s definitely look like the "sleepy" trace, but I would like confirmation from the best and brightest here. I've also include a log of my warmup period at idle. My plot was taken with engine temps around 150 F to 160 F
Following are two images, the first one was posted by jimmyblue and the second is mine (titled "untitled.png").
I swapped a 1998 LS1 A4 into my 1972 240z. The modifications include a 3-in. intake pipe to a 3.5-in. cone K&N filter, LS6 intake modified for the LS1 coolant tubes (I shaved the ribbing), ported and polished throttle body, JTR/Sanderson shorty headers. The O2s are located a few inches down from the collectors.
My issues are as follows. During the initial warmup period after a cold start, the car runs great. Once the ECT hits 94 F and the STFTs are enabled, the idle quality drops a little until 149 F at which time the LTFTs are enabled. Once the car moves to the LTFTs, I start to get random popping out of the exhaust.
My LTFTs once warmed up peg at 22.7 for B1 and 16.4 for B2. They hit those values and do not waver. My STFTs at that point fluctuate around 0. I do not have any codes. I've been battling this since August 2011. I do not drive the car all that often as a result of this issue and have not really had the time to troubleshoot it until now.
Thank you.
Following are two images, the first one was posted by jimmyblue and the second is mine (titled "untitled.png").
I swapped a 1998 LS1 A4 into my 1972 240z. The modifications include a 3-in. intake pipe to a 3.5-in. cone K&N filter, LS6 intake modified for the LS1 coolant tubes (I shaved the ribbing), ported and polished throttle body, JTR/Sanderson shorty headers. The O2s are located a few inches down from the collectors.
My issues are as follows. During the initial warmup period after a cold start, the car runs great. Once the ECT hits 94 F and the STFTs are enabled, the idle quality drops a little until 149 F at which time the LTFTs are enabled. Once the car moves to the LTFTs, I start to get random popping out of the exhaust.
My LTFTs once warmed up peg at 22.7 for B1 and 16.4 for B2. They hit those values and do not waver. My STFTs at that point fluctuate around 0. I do not have any codes. I've been battling this since August 2011. I do not drive the car all that often as a result of this issue and have not really had the time to troubleshoot it until now.
Thank you.
01-01-2012, 10:30 PM
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Thanks for the quick response, but are you sure? They look nothing like the "happy" O2 plot, they are definitely not switching as fast as the "happy" O2 plot. I just saw the attached plot that shows a different set of happy O2s as well. jimmy's were spiky whereas the following are more square, but you can clearly see in both cases that there are no long flat spots as in my plot. I am not trying to argue with you about this, but everything I've read and seen points to the O2s being slow.
01-01-2012, 10:34 PM
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Fuel pressure at the rail is 58 psi and does not waver and the FP regulator is back by the tank (using Corvette filter/FPR). The MAF sensor is stock and was recently cleaned (it was doing this before and after the cleaning). The PCM has not been tuned save for EGR/AIR/VATs/COT.
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01-01-2012, 10:50 PM
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The trims have been cleared numerous times, but I have not disconnected the MAF yet. I was going to do that tomorrow (clear trims and disconnect the MAF).
I was fighting exhaust leaks and thought they were the cause of the problem. Burned out composite gaskets (since went with aluminum), poor welding by the exhaust shop, etc. Once I fixed these the car runs better, but I am still getting the random popping at idle once fully warmed-up. I've since fixed the exhaust leaks and planned on hunting for vacuum leaks (yet again) tomorrow.
I was fighting exhaust leaks and thought they were the cause of the problem. Burned out composite gaskets (since went with aluminum), poor welding by the exhaust shop, etc. Once I fixed these the car runs better, but I am still getting the random popping at idle once fully warmed-up. I've since fixed the exhaust leaks and planned on hunting for vacuum leaks (yet again) tomorrow.
01-02-2012, 11:12 AM
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Fairly certain that it is not leaking, but I was going to check that as well. If there was a vacuum leak, then it would not matter if my car was in open or closed loop.
Before this thread gets derailed, I am really hoping someone will confirm whether or not my O2s are sleepy or not. Everything I've read so far and the images I've seen leads me to believe that is the case. I am not saying I've found the root cause as I may have an exhaust or vacuum leak.
Before this thread gets derailed, I am really hoping someone will confirm whether or not my O2s are sleepy or not. Everything I've read so far and the images I've seen leads me to believe that is the case. I am not saying I've found the root cause as I may have an exhaust or vacuum leak.
01-02-2012, 04:51 PM
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Attached is a log where I disconnected the MAF and reset the trims. Further in the scan I enabled open loop and then enable closed loop again.
You can see the O2 response at times appears ok, then they fall back into that "sleepy" mode where I get long flat spots between peaks.
You can see the O2 response at times appears ok, then they fall back into that "sleepy" mode where I get long flat spots between peaks.
01-07-2012, 09:58 PM
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It turns out that they are only sleepy at idle. Logs of the O2 sensors under load shows nice, quick switching activity. I am having the same issue as many people with LS1 swaps: 1.75-in. diameter shorty headers, 2.5-in. exhaust and no cats makes for rather cool exhaust temps at idle. My O2s then think the car is lean, my STFTs and LTFTs shoot to +25, and the car starts backfiring. As soon as start moving again, it back fires a bit until the O2s correct everything.
01-08-2012, 06:39 AM
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It turns out that they are only sleepy at idle. Logs of the O2 sensors under load shows nice, quick switching activity. I am having the same issue as many people with LS1 swaps: 1.75-in. diameter shorty headers, 2.5-in. exhaust and no cats makes for rather cool exhaust temps at idle. My O2s then think the car is lean, my STFTs and LTFTs shoot to +25, and the car starts backfiring. As soon as start moving again, it back fires a bit until the O2s correct everything.
01-08-2012, 02:58 PM
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One log file is in the original post below the pictures. The log is of an idle session only from a cold start if I remember correctly (HP Tuners is on my laptop). Shoot is an incorrect term. They steadily climb to +20 to +25 when I come to a stop and the car starts backfiring. I believe that the O2s slow down considerably which is the cause of the problem. There are longish periods where they are flat. No air leaks, no vacuum leaks and I've checked numerous times.
I tried a few tricks today. I changed the Closed Loop Proportional vs Airflow mode from 128 to 500. This woke the O2s up a bit and while not like under load, my STFTs were +8 to +15. I also dropped my O2 switch points down to 350 for modes 0, 2 and 4 but I did not see any change in O2 activity so I switched them back.
I also tried the PE trick to force open loop at idle. This worked beautifully and I will probably go this route once my VE tuning is completed.
I tried a few tricks today. I changed the Closed Loop Proportional vs Airflow mode from 128 to 500. This woke the O2s up a bit and while not like under load, my STFTs were +8 to +15. I also dropped my O2 switch points down to 350 for modes 0, 2 and 4 but I did not see any change in O2 activity so I switched them back.
I also tried the PE trick to force open loop at idle. This worked beautifully and I will probably go this route once my VE tuning is completed.
01-09-2012, 11:37 AM
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Thank you for taking the time to look at the log. Turning off my LTFTs was the first thing I tried. I noticed a small improvement, but the STFTs still climbed up to +20 to +25. They climbed whenever the O2 sensor flatlined.
As I stated earlier, I tried a few tricks such as modifying the Closed Loop Proportional vs Airflow mode from 128 to 500 for the first 3 modes. This woke the O2s up a bit and while not like under load, my STFTs were +8 to +15. I did not get nearly the amount of backfiring as I did before. I also dropped my O2 switch points down to 350 for modes 0, 2 and 4 but I did not see any change in O2 activity so I switched them back. I may try lowering the switchpoint some more (300ish per a post by jimmyblue in the archives) to see if that helps.
I also tried the PE trick to force open loop at idle. This worked beautifully and I will probably go this route once my VE tuning is completed.
As I stated earlier, I tried a few tricks such as modifying the Closed Loop Proportional vs Airflow mode from 128 to 500 for the first 3 modes. This woke the O2s up a bit and while not like under load, my STFTs were +8 to +15. I did not get nearly the amount of backfiring as I did before. I also dropped my O2 switch points down to 350 for modes 0, 2 and 4 but I did not see any change in O2 activity so I switched them back. I may try lowering the switchpoint some more (300ish per a post by jimmyblue in the archives) to see if that helps.
I also tried the PE trick to force open loop at idle. This worked beautifully and I will probably go this route once my VE tuning is completed.
