7427 $0D Not Going Into Closed Loop

Been scratching my head on this for awhile, finally thought I would pose my issue to this group for some assistance. I have a TBI system installed on a 78 Corvette, powered by a 16197427 PCM. Been running great the last few years. Past couple months, I noticed some serious stumbling once the car heated up. Turned out my coil had come loose from its riveted mount and was causing lots of problems. Swapping in a good used coil made it run 10x better.

I had it hooked into TunerPro and noticed it was not entering closed loop. Sometimes the flag would turn very briefly to Closed, then the next moment back to Open. I watched the oxygen sensor readout and it looked really, really slow. Knowing that the PCM was looking for an O2 reading as part of the parameters to enter Closed Loop, I purchased another (Bosch 13077) and installed today. Took it on a 10 minute test drive and it still did not enter Closed Loop.

Can anyone list the parameters for closed loop operation? I know that Coolant Temp must be at a certain threshold and run time. Is there something I'm missing?

Attached is the current .bin file that the car is using, I'd greatly appreciate any comments and thoughts.

Thanks!

I should also add that the coolant temperature reading in TunerPro is spot on, around 200 degrees when at operating temp. Also, there is no check engine light being lit.

You also need O2 switching. Look at your O2 sensor data. I'll have to view your bin to see what your calibration is like

Brian

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Originally Posted by sturgillbd

You also need O2 switching. Look at your O2 sensor data. I'll have to view your bin to see what your calibration is like

Brian

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Agreed. I was reading back thru the pdf manual from years ago, oxygen sensor cross counts, or something to that effect. Will fire up the car and check it out. Thanks!

Finally was able to get in the car long enough to record a log while driving. Hopefully I'm attaching it correctly? This is with a new oxygen sensor (Bosch 13077). I'm concerned that while holding at steady speed (approximately 40mph), the O2 reading is flat. Might be totally normal? I watched the O2 cross counts, that seemed ok, but again stayed flat for coasting sections. Any guidance much appreciated.

Your "Closed Loop Idle" is checked. When I use "compare" to other bins, it is not checked. Your House Run xdl, closed loop flashes for a fraction of a second and purdy much stays open loop the entire log. I'm a little concerned that the log appears glitchy with alot of data swings???

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Originally Posted by stew86MCSS396

Your "Closed Loop Idle" is checked. When I use "compare" to other bins, it is not checked. Your House Run xdl, closed loop flashes for a fraction of a second and purdy much stays open loop the entire log. I'm a little concerned that the log appears glitchy with alot of data swings???

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Thanks for spotting the Closed Loop Idle flag. I will check that out and experiment.

You are right on the noise in the signal. I've seen that before on previous tunes and logs. My thoughts were that it must be something in the cable or auto prom as I could feel nothing causing disruption in the operation of the car. Is that a logical assumption?

Trying out a new computer for tuning, an older HP laptop that is useless for modern work. Runs TunerPro just fine, and I'm a little less worried about it crashing versus the cool RCA tablet/computer thing I've used for years.

Made a new datalog with this computer and thought I'd post it for anyone with guidance. Still the same "noise" and glitches in the datastream, and the car will briefly enter Closed Loop then snap right out. By watching the bitmasks, I could see that the ignition was even seen as going switching briefly off.

These issues were not present when I initially tuned the car, but something is causing issues, at least with the datastream. The car runs great, no hesitating or stumbling.

Any recommendations on where to start on the "noise" reduction? I searched through the site and could not find info, so any expert advice would be greatly appreciated.

Thanks!
Matt

I solved my glitchy data issue by adding a pause in the mode 1 commands sent by the adx file. See attached screenshots. Edit your adx file by clicking acquisition, edit definition, then commands . You are not entering closed loop because you have no real O2 activity. Faulty O2 sensor or improperly wired ?
Hope this helps,
Brian

Thanks Brian! I will definitely check if the steps you list help with the glitches. Something is definitely going on - I remembered I had a file of my test drive when I first installed the system, so loaded that up to compare. Sure enough, the data is nice and clean. And the oxygen sensor is performing exactly as it should, with the car going into closed loop.

When I first spotted the failure to go into closed loop, I watched and thought it could be the oxygen sensor. Brand new Bosch unit and it is performing the exact same as the original one (that worked until whenever I got into investigating the issues). Still have a few days to ship back to Amazon for a replacement.

Attached is the log of the test run when everything was running like it should. If I still get glitches after making changes that you listed, I'm going to start looking for RF noise in the engine bay.

Looks like something went off the rails in the past twelve months. I found a log from almost exactly a year ago (July 12, 2020) where I was checking on the function of the EGR as it might relate to the bogging issue I was having (turned out to be bad coil). Nice, clean data trace along with a good oxygen sensor signal. At least narrowing down the time frame where something might be amiss. I might need to start doing more regular logs!

Attachment 16875
Attachment 16876

Quote:

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Originally Posted by sturgillbd

I solved my glitchy data issue by adding a pause in the mode 1 commands sent by the adx file. See attached screenshots. Edit your adx file by clicking acquisition, edit definition, then commands . You are not entering closed loop because you have no real O2 activity. Faulty O2 sensor or improperly wired ?
Hope this helps,
Brian

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Added the pause command (thank you for the screenshots, those REALLY helped!) and the noise was greatly reduced. Log much cleaner. On first drive, was running poorly - bogging down and stumbling upon acceleration. Turned off, started back up a few minutes later and it ran like normal. Fortunately I had the laptop on board, was able to log both sessions. I'm leaning towards an ignition issue. Have a spare coil to try out.