Scan9495 Observations?
07-26-2018, 07:52 AM
#1
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Scan9495 Observations?
Looking for observations of a datalog I made yesterday morning with Scan9495. I hope I've inserted it correctly.
DLOG-2018Jul25-075007-2G1FP32P9S2159594.csv
What I see is that I'm running rich pretty much the whole time. This run was mainly all interstate at around 80 MPH. I didn't do any WOT.
1st steady interstate time is at about 7:53 TOD for about 7 minutes. Then again at about 8:15 TOD for about 7 minutes.
Is it normal for O2s to jump around voltage wise like mine do? They are standard narrow band that I replaced a couple of years ago.
What else do you observe?
As per my sig this is with EGR disabled and blocked off, mid-length headers, mild Comp Cam, no headwork or engine work, 52mm Holley TB, K&N FIPK, Borla exhaust with no cat.
TIA
DLOG-2018Jul25-075007-2G1FP32P9S2159594.csv
What I see is that I'm running rich pretty much the whole time. This run was mainly all interstate at around 80 MPH. I didn't do any WOT.
1st steady interstate time is at about 7:53 TOD for about 7 minutes. Then again at about 8:15 TOD for about 7 minutes.
Is it normal for O2s to jump around voltage wise like mine do? They are standard narrow band that I replaced a couple of years ago.
What else do you observe?
As per my sig this is with EGR disabled and blocked off, mid-length headers, mild Comp Cam, no headwork or engine work, 52mm Holley TB, K&N FIPK, Borla exhaust with no cat.
TIA
07-26-2018, 08:46 AM
#2
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Re: Scan9495 Observations?
In closed loop the O2 sensor readings should cycle rapidly back and forth from lean (as low as 0.0xx volts) to rich (as high as 0.9xx volts). That's required to allow the monolithic catalytic converters to operate efficiently, breaking down (reducing) NOx to produce oxygen, and then using that oxygen to combine with CO to produce CO2, and with HC (unburned hydrocarbons) to produce CO2 and H2O.
I have a 20+ page LT1-specific scanner guide that explains a lot of the readings you see on a scanner. I've uploaded it here before. I'll see if I can find the link, or upload it again.
I'll take a look at your data log later today.
I have a 20+ page LT1-specific scanner guide that explains a lot of the readings you see on a scanner. I've uploaded it here before. I'll see if I can find the link, or upload it again.
I'll take a look at your data log later today.
07-26-2018, 08:49 AM
#3
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Re: Scan9495 Observations?
Thanks for the explanation Fred.
I believe I have your document if it's titled Scanmaster (sic).
I've been working on it. I'm still learning how to interpret the data (obviously).
I believe I have your document if it's titled Scanmaster (sic).
I've been working on it. I'm still learning how to interpret the data (obviously).
07-26-2018, 05:45 PM
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Re: Scan9495 Observations?
First you look at the “long term”. If it’s 128 it means the PCM calculation is supplying exactly the right amount of fuel to maintain the target 14.7:1 A/F ratio. When that is the case, the “short term” will move up and down above and below 128. It does that for the cat operation as described earlier. If you take an average over a long period of time, the short term should be averaging 128.
All this applies to a single “cell” at a time. The cells are memory registers where the learned long term fuel corrections are stored. There are 19 different cells. Cells 0 through 15 are arranged in a grid defined by RPM on one axis and engine load (MAP) on the other. Cell 0 is very low RPM and very low MAP. Cell 15 is very high RPM and very high MAP. Cell 16 represents closed throttle/0 MPH idle. Cell 18 is a mathematical combination of Cells 0-15, and is used (mostly) to fuel the engine when the PCM is operating in open loop (no O2 sensor feedback). Cell 17 is primarily used for deceleration (closed throttle).
More to follow.... I just don’t want to lose what I just typed on my iPad.
All this applies to a single “cell” at a time. The cells are memory registers where the learned long term fuel corrections are stored. There are 19 different cells. Cells 0 through 15 are arranged in a grid defined by RPM on one axis and engine load (MAP) on the other. Cell 0 is very low RPM and very low MAP. Cell 15 is very high RPM and very high MAP. Cell 16 represents closed throttle/0 MPH idle. Cell 18 is a mathematical combination of Cells 0-15, and is used (mostly) to fuel the engine when the PCM is operating in open loop (no O2 sensor feedback). Cell 17 is primarily used for deceleration (closed throttle).
More to follow.... I just don’t want to lose what I just typed on my iPad.
Last edited by Injuneer; 07-26-2018 at 05:56 PM.
07-26-2018, 06:21 PM
#6
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Re: Scan9495 Observations?
I'm trying to use Vemaster to setup up the cells in Speed Density. I've disconnected the MAF and done a couple of runs, and processed with Vemaster. I've loaded the two runs into Tunercat to compare them. E.G. the first Vemaster modded file then the 2nd Vemaster modified file. Tunercat Compare Files is not showing a difference in the cells. However, I'm definitely not at 128s steady and across the BLMs so I would think there are more adjustments to be made.
I've got Vemaster ver. 1.33 that I downloaded from LT1PCMTuning.com, the only place I've been able to find a good link to the program.
On a forum I saw one person was getting no results from the processing through Vemaster because he did not have Vemaster EE for the EE prom. When I install Vemaster it doesn't ask me for my definition file.
Bottom line I don't know if I'm accomplishing anything or not.
Anyone have any insights?
I've got Vemaster ver. 1.33 that I downloaded from LT1PCMTuning.com, the only place I've been able to find a good link to the program.
On a forum I saw one person was getting no results from the processing through Vemaster because he did not have Vemaster EE for the EE prom. When I install Vemaster it doesn't ask me for my definition file.
Bottom line I don't know if I'm accomplishing anything or not.
Anyone have any insights?
07-27-2018, 10:10 AM
#7
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Re: Scan9495 Observations?
Appears you have decided on a path forward to correct what you perceive as the "problem". Do you want me to look further at your file, or am I just wasting my time?
07-27-2018, 04:15 PM
#9
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Re: Scan9495 Observations?
It’s a big file, almost 10,000 lines of data. First thing that jumped out at me is the unusually high number of lines that contain bad data. Wouldn't be anything unusual to see a half dozen lines with obvious errors. That can be the result of interference on the data link connector data line. But this file has dozens of lines that I have marked to identify them, and I haven’t gone through that much of it yet. At this point I'll ask GaryDoug to look at it to see if theses errors, occurring one to twenty seconds apart, are symptomatic of a PCM problem.
Looking at the data that appears to be valid, most of the frequently used LTFT cells are subtracting 10 to 15% of the “normal” fuel to prevent it from running rich. Some imbalance from left to right bank, but not major. The key, before you try to correct things in the program, is to look for possible external causes. Possibilities:
- faulty or dirty MAF sensor.
- messed up calibration table for MAF sensor
- excessive fuel pressure
- multiple worn/slow injectors
- incorrect injector flow constant
- incorrect injector offsets
- faulty O2 sensors or wiring
- fuel pressure regulator leaking fuel into the intake manifold
Who tuned it for the cam? Have you changed anything after the tune was done - injector data, MAF table, etc.? To me, it's a serious mistake to try and start changing things in the program before you verify everything else is OK.
I"ll keep looking, but the repeated errors in the data log are making it difficult. Having the possibility that the tune has been further corrupted in an attempt to band-aid the possible problem just adds to the frustration.
Looking at the data that appears to be valid, most of the frequently used LTFT cells are subtracting 10 to 15% of the “normal” fuel to prevent it from running rich. Some imbalance from left to right bank, but not major. The key, before you try to correct things in the program, is to look for possible external causes. Possibilities:
- faulty or dirty MAF sensor.
- messed up calibration table for MAF sensor
- excessive fuel pressure
- multiple worn/slow injectors
- incorrect injector flow constant
- incorrect injector offsets
- faulty O2 sensors or wiring
- fuel pressure regulator leaking fuel into the intake manifold
Who tuned it for the cam? Have you changed anything after the tune was done - injector data, MAF table, etc.? To me, it's a serious mistake to try and start changing things in the program before you verify everything else is OK.
I"ll keep looking, but the repeated errors in the data log are making it difficult. Having the possibility that the tune has been further corrupted in an attempt to band-aid the possible problem just adds to the frustration.
07-27-2018, 05:22 PM
#10
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Re: Scan9495 Observations?
Thanks for the check list -
- faulty or dirty MAF sensor - I'll check and clean
- messed up calibration table for MAF sensor - I haven't made any changes
- excessive fuel pressure - I tested a year or two ago and it was at spec. I'll check again
- multiple worn/slow injectors - The injectors were tested, cleaned and retested in 2015. I've attached the report.
- incorrect injector flow constant - I've not changed this table
- incorrect injector offsets - I've not changed this table
- faulty O2 sensors or wiring - always a possibility, I'll be checking
- fuel pressure regulator leaking fuel into the intake manifold - I'll check
The errors may be due to my using a Bluetooth ALDL adapter to my laptop. I have an ALDL to USB cable but I've not had any success getting it to connect to the ECM. I've emailed Gary and the FTDI folks on this problem. I plan to purchase a new ALDL to USB setup soon.
The current tune was done by CincySpeed in Cincinnati in January 2016. The car was dyno'd and tuned. The only change I've made is to correct the speedometer. This is the tune in place for the datalog I posted.
I previously had a tune from PCMforLess. I have PCM readings for my car back to the day I purchased it and can re-program the computer with any of them.
Perhaps it would be best for me to go over the list you provided, get a direct connect cable, and get another datalog for review.
- faulty or dirty MAF sensor - I'll check and clean
- messed up calibration table for MAF sensor - I haven't made any changes
- excessive fuel pressure - I tested a year or two ago and it was at spec. I'll check again
- multiple worn/slow injectors - The injectors were tested, cleaned and retested in 2015. I've attached the report.
- incorrect injector flow constant - I've not changed this table
- incorrect injector offsets - I've not changed this table
- faulty O2 sensors or wiring - always a possibility, I'll be checking
- fuel pressure regulator leaking fuel into the intake manifold - I'll check
The errors may be due to my using a Bluetooth ALDL adapter to my laptop. I have an ALDL to USB cable but I've not had any success getting it to connect to the ECM. I've emailed Gary and the FTDI folks on this problem. I plan to purchase a new ALDL to USB setup soon.
The current tune was done by CincySpeed in Cincinnati in January 2016. The car was dyno'd and tuned. The only change I've made is to correct the speedometer. This is the tune in place for the datalog I posted.
I previously had a tune from PCMforLess. I have PCM readings for my car back to the day I purchased it and can re-program the computer with any of them.
Perhaps it would be best for me to go over the list you provided, get a direct connect cable, and get another datalog for review.
07-28-2018, 12:36 PM
#11
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Re: Scan9495 Observations?
The error lines in the log file might be due to a failing PCM or cable or excessive loading of the data line by the ABS or SIR modules. The only way to know is to put a scope on the line and see the voltage levels. But I am not sure why the program does not reject the data line and re-initiate the connection unless the PCM is reporting a bogus passing checksum as well. It might help to see the Comms log file.
07-28-2018, 12:54 PM
#12
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Re: Scan9495 Observations?
I don't think it is the ABS or SIR as I have not had these enabled during the datalogging. Could they still affect the logging if not enabled?
I can enable Comms next time I do a log. I will say that ALDLDroid does show Checksum errors when I use it.
I can enable Comms next time I do a log. I will say that ALDLDroid does show Checksum errors when I use it.
07-28-2018, 01:01 PM
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Re: Scan9495 Observations?
The ABS and SIR modules are physically connected to the same data line as the PCM. You don't have to be scanning them for that to have an effect. You could just measure the DC voltage at the data pin in the DLC while the ignition is on. The reading will jump around a bit but you should be able to see the general level, which should be above 2.5 volts.
07-28-2018, 01:03 PM
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Re: Scan9495 Observations?
You don;t have to be using a scan for the ABS and SIR for those to have an effect. They are physically connected to the PCM data line. Measure the voltage at the data line in the DLC while the ignition switch is on. It will normally jump a bit but should be generally above 2.5 volts DC.
edit: ooops, my last post didn't appear to take so I made another one. Must have been slow to post.
edit: ooops, my last post didn't appear to take so I made another one. Must have been slow to post.
Last edited by GaryDoug; 07-28-2018 at 04:34 PM.
07-28-2018, 04:08 PM
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Re: Scan9495 Observations?
Another piece of the puzzle, possibly pointing to the PCM.
In several instances, the end of the defective data line shows DTC 86. I assumed this was just a bogus code, because it isn’t referenced in the factory manual. But I did a Google search on GM OBD1 Trouble Code 86, and found it is a code (at least in some other vehicles) for:
https://repairpal.com/gm-obd-code-86
KYWes: is the engine experiencing any noticeable “hiccups” that might correspond to these data faults.
In several instances, the end of the defective data line shows DTC 86. I assumed this was just a bogus code, because it isn’t referenced in the factory manual. But I did a Google search on GM OBD1 Trouble Code 86, and found it is a code (at least in some other vehicles) for:
https://repairpal.com/gm-obd-code-86
KYWes: is the engine experiencing any noticeable “hiccups” that might correspond to these data faults.