Only getting Positive fuel trims
07-07-2019, 01:16 PM
#31
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Re: Only getting Positive fuel trims
Originally Posted by Injuneer
Conclusion at this point is either the program, the PCM (unlikely) or the scan software is screwed up.
It could be some other sensor, but if that were the case I'd expect to be able to see it in the log. An issue with the scan software could hide that, but that would mean two simultaneous issues manifesting as one (since an issue with the software couldn't possibly manifest in actual vehicle issues), which is very unlikely.
07-07-2019, 01:28 PM
#32
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Re: Only getting Positive fuel trims
I'm leaning towards the PCM, honestly. If it were the program, it wouldn't only be wrong after a warm restart. Same if it were the scan software.
It could be some other sensor, but if that were the case I'd expect to be able to see it in the log. An issue with the scan software could hide that, but that would mean two simultaneous issues manifesting as one (since an issue with the software couldn't possibly manifest in actual vehicle issues), which is very unlikely.
It could be some other sensor, but if that were the case I'd expect to be able to see it in the log. An issue with the scan software could hide that, but that would mean two simultaneous issues manifesting as one (since an issue with the software couldn't possibly manifest in actual vehicle issues), which is very unlikely.
At this point, I don't think you can rule anything out.
And the fact that I've had this setup in my car for over a year and it took this long too be this consistent.
07-07-2019, 01:30 PM
#33
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Re: Only getting Positive fuel trims
I appreciate all the hours of help you have put in trying to figure out this mess, injuneer.
I won't give up just yet, and I'll continue to post results on this thread, but don't feel obligated to keep investigating. I was just hoping my untrained(ish) eyes were missing something that was right in front of my face.
I won't give up just yet, and I'll continue to post results on this thread, but don't feel obligated to keep investigating. I was just hoping my untrained(ish) eyes were missing something that was right in front of my face.
07-08-2019, 01:37 AM
#34
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Re: Only getting Positive fuel trims
Alright, finally made some progress here.
It's something in the tune. I flashed a bone stock cal file into the car and have fuel trims all the time. It also doesn't do this crazy lurching stuff at low speeds. Time to slowly start adding his parameters in and flashing and see what's making them disappear.
Also, time for a new tuner.
It's something in the tune. I flashed a bone stock cal file into the car and have fuel trims all the time. It also doesn't do this crazy lurching stuff at low speeds. Time to slowly start adding his parameters in and flashing and see what's making them disappear.
Also, time for a new tuner.
07-08-2019, 09:16 AM
#36
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Re: Only getting Positive fuel trims
Based on the link you posted in #28, do not attempt to defeat the EVAP (CCP) system. That seems to correlate well to the issues I found - dropping into Cell 16 when the engine is not idling, and failing to operate in 17 and 18 when it is supposed to. I guess you never included the EVAP duty cycle in the data logs because it had been deleted.
I never recommend deleting the emissions, other than AIR. EGR and EVAP are useful on a street driven car, and don't hurt performance. Even after adding a parallel aftermarket ECU to control my nitrous assisted stroker, we kept all the emissions working with the stock PCM..... wasn’t easy, because it required extra/duplicate sensors to feed both computers. Wasn’t until I decided to take it off the street that I removed the AIR, EGR, and EVAP. Without the EVAP, there was always an intoxicating cloud of VP Fuels C16 vapor at the rear of the car when I wasn’t running pump gas.
I will repeat my recommendation on Moe Bailey. A friend of mine picked up a slightly modified 30th SS A4 convertible (trying to partially relive his earlier mid-life crises when he owned a similar 30th SS, and was running low 8’s at close to 170 MPH). He liked the new SS, but it was shifting way too late. He asked who could tweak the tune. Having seen that some of the old/reliable LT1 tuners stopped tuning the LT1, and that several people still tuning them were not getting good results, I told him to try Moe. That was based on a lot of positive feedback on ltxtech.com. When he got the PCM back and installed it, I got a three word text - “ spinnin’ and grinnin’ “. Not only were the shift problems solved, the engine ran smoother and made much better power.... with no problems. And they didn't even know what cam the previous owner had put in the engine.
I never recommend deleting the emissions, other than AIR. EGR and EVAP are useful on a street driven car, and don't hurt performance. Even after adding a parallel aftermarket ECU to control my nitrous assisted stroker, we kept all the emissions working with the stock PCM..... wasn’t easy, because it required extra/duplicate sensors to feed both computers. Wasn’t until I decided to take it off the street that I removed the AIR, EGR, and EVAP. Without the EVAP, there was always an intoxicating cloud of VP Fuels C16 vapor at the rear of the car when I wasn’t running pump gas.
I will repeat my recommendation on Moe Bailey. A friend of mine picked up a slightly modified 30th SS A4 convertible (trying to partially relive his earlier mid-life crises when he owned a similar 30th SS, and was running low 8’s at close to 170 MPH). He liked the new SS, but it was shifting way too late. He asked who could tweak the tune. Having seen that some of the old/reliable LT1 tuners stopped tuning the LT1, and that several people still tuning them were not getting good results, I told him to try Moe. That was based on a lot of positive feedback on ltxtech.com. When he got the PCM back and installed it, I got a three word text - “ spinnin’ and grinnin’ “. Not only were the shift problems solved, the engine ran smoother and made much better power.... with no problems. And they didn't even know what cam the previous owner had put in the engine.
Last edited by Injuneer; 07-08-2019 at 10:15 AM.
07-08-2019, 03:09 PM
#37
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Re: Only getting Positive fuel trims
Based on the link you posted in #28, do not attempt to defeat the EVAP (CCP) system. That seems to correlate well to the issues I found - dropping into Cell 16 when the engine is not idling, and failing to operate in 17 and 18 when it is supposed to. I guess you never included the EVAP duty cycle in the data logs because it had been deleted.
I never recommend deleting the emissions, other than AIR. EGR and EVAP are useful on a street driven car, and don't hurt performance. Even after adding a parallel aftermarket ECU to control my nitrous assisted stroker, we kept all the emissions working with the stock PCM..... wasn’t easy, because it required extra/duplicate sensors to feed both computers. Wasn’t until I decided to take it off the street that I removed the AIR, EGR, and EVAP. Without the EVAP, there was always an intoxicating cloud of VP Fuels C16 vapor at the rear of the car when I wasn’t running pump gas.
I will repeat my recommendation on Moe Bailey. A friend of mine picked up a slightly modified 30th SS A4 convertible (trying to partially relive his earlier mid-life crises when he owned a similar 30th SS, and was running low 8’s at close to 170 MPH). He liked the new SS, but it was shifting way too late. He asked who could tweak the tune. Having seen that some of the old/reliable LT1 tuners stopped tuning the LT1, and that several people still tuning them were not getting good results, I told him to try Moe. That was based on a lot of positive feedback on ltxtech.com. When he got the PCM back and installed it, I got a three word text - “ spinnin’ and grinnin’ “. Not only were the shift problems solved, the engine ran smoother and made much better power.... with no problems. And they didn't even know what cam the previous owner had put in the engine.
I never recommend deleting the emissions, other than AIR. EGR and EVAP are useful on a street driven car, and don't hurt performance. Even after adding a parallel aftermarket ECU to control my nitrous assisted stroker, we kept all the emissions working with the stock PCM..... wasn’t easy, because it required extra/duplicate sensors to feed both computers. Wasn’t until I decided to take it off the street that I removed the AIR, EGR, and EVAP. Without the EVAP, there was always an intoxicating cloud of VP Fuels C16 vapor at the rear of the car when I wasn’t running pump gas.
I will repeat my recommendation on Moe Bailey. A friend of mine picked up a slightly modified 30th SS A4 convertible (trying to partially relive his earlier mid-life crises when he owned a similar 30th SS, and was running low 8’s at close to 170 MPH). He liked the new SS, but it was shifting way too late. He asked who could tweak the tune. Having seen that some of the old/reliable LT1 tuners stopped tuning the LT1, and that several people still tuning them were not getting good results, I told him to try Moe. That was based on a lot of positive feedback on ltxtech.com. When he got the PCM back and installed it, I got a three word text - “ spinnin’ and grinnin’ “. Not only were the shift problems solved, the engine ran smoother and made much better power.... with no problems. And they didn't even know what cam the previous owner had put in the engine.
07-09-2019, 04:10 PM
#38
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Re: Only getting Positive fuel trims
Figured it out.
It's the initial startup afr enrich VS coolant temp table.
I started with a bone stock tune. Trims worked fine.
At that point, I kept loading and flashing my tuners parameters in groups until I was able to duplicate the problem. After about 75% of the parameters were loaded in, I finally found that this table is what is screwing it up.
I then took my tuners calibration file and ONLY changed this table back to the stock settings. (Was altered) Works like it should. I wonder if there's some sort of parameter in JET/Tunercat that hasn't been added to the program that feeds/depends off of this table or something. Either way, I finally figured it out.
It's the initial startup afr enrich VS coolant temp table.
I started with a bone stock tune. Trims worked fine.
At that point, I kept loading and flashing my tuners parameters in groups until I was able to duplicate the problem. After about 75% of the parameters were loaded in, I finally found that this table is what is screwing it up.
I then took my tuners calibration file and ONLY changed this table back to the stock settings. (Was altered) Works like it should. I wonder if there's some sort of parameter in JET/Tunercat that hasn't been added to the program that feeds/depends off of this table or something. Either way, I finally figured it out.
07-09-2019, 04:40 PM
#39
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Re: Only getting Positive fuel trims
What specifically was screwed up in that table? Once the coolant reaches a threshold temperature, that table should be ignored. It shouldn’t even be in closed loop during cold start enrichment.
In the second 1/2 of the log where you indicated the fuel trims disappeared, the coolant was 180°F +/-5°. And your data log showed the target A/F ratio as 14.7:1, except when it appears it briefly entered PE mode. If the PCM was targeting anything other than 14.7:1, fuel trims (learning) would be disabled. That would have shown up as the flag I mentioned earlier. Did you ever test or produce a log with that flag (“fuel trim learn”)?
In the second 1/2 of the log where you indicated the fuel trims disappeared, the coolant was 180°F +/-5°. And your data log showed the target A/F ratio as 14.7:1, except when it appears it briefly entered PE mode. If the PCM was targeting anything other than 14.7:1, fuel trims (learning) would be disabled. That would have shown up as the flag I mentioned earlier. Did you ever test or produce a log with that flag (“fuel trim learn”)?
07-09-2019, 07:07 PM
#40
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Re: Only getting Positive fuel trims
I'm not sure what exactly in the table is screwing things up, other than when I use the unaltered stock table my fuel trims show up and work like they are supposed to.
I feel like there could be an error in the code behind the table. I guess it was a later addition to tunercat so it might not have got all the kinks worked out.
I feel like this is why my car will show trims after I leave it sit for awhile, {it falls in a lower cell of the coolant temp}
And then when I restart it, it's already up to operating temp. I never did restart the car right away when it was still cold. It was always up to operating temp.
Logically, it doesn't make sense, no, but there could be an error in the way the table is made.
And I could never figure out how to turn the flag on for fuel trim enable.
I will do a few more tests. I'll find what my coolant temp is when I immediately turn on the car after it's been sitting and set the whole enrich afr table to that number.
Also, I'll try restarting the car immediately versus letting get to temp. I really feel I'm onto something here.
I feel like there could be an error in the code behind the table. I guess it was a later addition to tunercat so it might not have got all the kinks worked out.
I feel like this is why my car will show trims after I leave it sit for awhile, {it falls in a lower cell of the coolant temp}
And then when I restart it, it's already up to operating temp. I never did restart the car right away when it was still cold. It was always up to operating temp.
Logically, it doesn't make sense, no, but there could be an error in the way the table is made.
And I could never figure out how to turn the flag on for fuel trim enable.
I will do a few more tests. I'll find what my coolant temp is when I immediately turn on the car after it's been sitting and set the whole enrich afr table to that number.
Also, I'll try restarting the car immediately versus letting get to temp. I really feel I'm onto something here.
Last edited by slikrider20; 07-09-2019 at 07:12 PM.
07-09-2019, 07:18 PM
#41
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Re: Only getting Positive fuel trims
The logic turns on learning enabled, when the coolant reaches a (variable) minimum temperature, the O2 sensors are showing activity because they are hot enough to work, and a timer (typically 206-seconds) times out. Maybe coolant temp required for closed loop/learning enabled is related to the coolant temp in the table you found. After a cold start, closed loop seems to occur at 140°F, but at other times I've seen it much lower.
07-09-2019, 08:03 PM
#42
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Re: Only getting Positive fuel trims
I think that is just startup enrichment. I wouldn't think it should be jacking up your fuel trims unless it's being used to try and to compensate for some kind of fueling issue.
Can you post up the tune in question? I'll download it and compare it to my stock tune and my CC503 tune.
You can generate a report of two program differences with Jet DST.
If your mods are what is listed in your sig, you shouldn't need anything crazy in the tune to get that thing to run fine. You've pretty much got the same as me according to your sig.....with the exception of emissions...I've still got full emissions.
What injectors are you running?
Can you post up the tune in question? I'll download it and compare it to my stock tune and my CC503 tune.
You can generate a report of two program differences with Jet DST.
If your mods are what is listed in your sig, you shouldn't need anything crazy in the tune to get that thing to run fine. You've pretty much got the same as me according to your sig.....with the exception of emissions...I've still got full emissions.
What injectors are you running?
Last edited by ACE1252; 07-09-2019 at 11:05 PM.
07-11-2019, 12:44 AM
#44
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Re: Only getting Positive fuel trims
Nothing jumps out at me in the tune that would cause this problem. If changing that table back to stock fixed it, I'd say leave it set to stock values. I really don't see any value in not having some startup enrichment.
One thing about that table....it's never 0.0 in the stock programming(like with your problematic tune). It may be that a value of 0 on initial startup, at a temp above 56C(132F) does something odd with the PCM code.
With his problematic tune, that table is all zeros above 56C.
If I get some free time, I may set that table to all zeros in my PCM, warm it up, shut it down, then see if it does the same thing as yours.
LoL, but I may leave well enough alone as not to screw something up.
One thing about that table....it's never 0.0 in the stock programming(like with your problematic tune). It may be that a value of 0 on initial startup, at a temp above 56C(132F) does something odd with the PCM code.
With his problematic tune, that table is all zeros above 56C.
If I get some free time, I may set that table to all zeros in my PCM, warm it up, shut it down, then see if it does the same thing as yours.
LoL, but I may leave well enough alone as not to screw something up.
Last edited by ACE1252; 07-11-2019 at 12:50 AM.
07-11-2019, 01:12 AM
#45
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Re: Only getting Positive fuel trims
Yeah, definitely has to be something along those lines...I mean that is why you'd think I have to let my car sit for so long (versus resetting PCM) in order to get the trims back.
Obviously the car is so much more enjoyable to drive with the trims all working. It doesn't even feel like the same car.
Did you happen to ever dyno your Z? I've heard people with similar mods making around 350-375rwhp but I haven't got mine dynoed just yet. If this problem stays away for awhile i'll have to set something up at my local shop.
Obviously the car is so much more enjoyable to drive with the trims all working. It doesn't even feel like the same car.
Did you happen to ever dyno your Z? I've heard people with similar mods making around 350-375rwhp but I haven't got mine dynoed just yet. If this problem stays away for awhile i'll have to set something up at my local shop.