Lean Condition - Stuck Commanded AFR
11-15-2017, 10:02 PM
#1
Registered
Thread Starter
Join Date: Feb 2009
Posts: 13
Likes: 0
Received 0 Likes
on
0 Posts
Lean Condition - Stuck Commanded AFR
First, apologies if this thread is posted in the wrong forum. I could not post in the Series I Trouble Shooting, and I see many queries in the new member forum.
-----------------
I have been dealing with a lean condition for several months (no codes though). The WOT/Open Loop AFR (past +7k RPM ) is about 13-14, and the car feels sluggish. Last year AFR was about 12.4 on similar RPM’s. My car is an NA 2004 MT, and I mainly use it on the track. The engine was rebuilt early this year and it has about 1800 miles.
I have taken quite a few troubleshooting steps without success. The troubleshooting so far has been:
Inspected fuel pump pressure (S2 pump). The pressures fluctuate 52-58 depending on fuel tank level and temperature. However, I have not seen any sudden decrease in pressure that could be correlated with lack of fuel delivery. See post on: https://www.rx8club.com/series-ii-af...5/#post4823391. Additionally, I got hold of a Kenne Bell BAP and I installed with a manual switch. I can see 1-2 psi pressure increase while the booster is ON and the measured voltage getting to the pump is 17.5 volts.
Inspected for vacuum leaks. I did both a smoke test as well as carburetor spray around the intake manifold and injectors. I found a couple of small leaks, one at the UIM/LIM union and another at the MAF O-ring. Fixed both with no changes to the symptoms.
Replaced spark plugs and switch back/forth between OEM C coil and cables (~10k miles on them) and BHR coils and Moroso cables (~30k miles on the kit). I have also tested all coils with an HEI spark tester. I haven’t found anything wrong with neither of the kits, nor I have seen changes to the overall lean condition with one kit or the other.
Inspected, cleaned and also switched the MAF sensor with an original MAF from another 2004 car (+100k miles car). I have also logged data at idle and 2500 RPM as per Mazda MAF inspection instructions:
Mazda Specs: Engine speed Engine load calculated value (WDS PID: LOAD)Intake MAF (WDS PID: MAF)
Idle after warm-up (no load) 18.0—25.0% (LOAD) 3.8—4.7 g/s (MAF)
2,500 rpm 13.5—19.5% (LOAD) 8.7—11.7 g/s (MAF)
The attached data logged diverge from the quoted specs above, however, I noticed no difference between the two MAF sensors, which may indicate that this is normal with the Racing Beat/Revi intake rather than the stock intake? (Perhaps changes to the intake tube diameter?) The MAF at WOT shows +200g/s.
Looking at data logs at the time and the symptoms I was more inclined to expect an electrical/electronic failure. Reason being, the commanded AFR and the LTFT were (and still are) stuck at fixed values).
The AFR was Lean, yes, but the Commanded AFR was pretty much fix at 15.37 (both open/closed loop) with small dips to 14.65 (same goes to Lambda). It’s like the PCM does not want to change the AFR at all.
The Short Term Fuel Trim seems ok, fluctuating under 20%, however, the Long Term Fuel Trim is set at zero and does not change. I have done many logs, done many cycles with the car, run 20-30 miles expecting a change and nothing.
So with this in mind and having the Racing Beat (RB) Flash Ren V1 on the PCM, I opted to send the PCM for inspection to RB to check if something could have been wrong. RB didn’t find anything abnormal with the PCM and advised me that was better to flash the PCM with Ren V3 due to the ported engine, something that didn’t seem to be causing issues in the past, however, I gave it a try and flashed to V3, but this did nothing solving the issue.
Replaced rear O2 sensor. The sensor went bad ages ago since the lack of cat and had no resistance between the two connection terminals. I wasn’t expecting this to be the silver bullet, but I wanted to make sure this didn’t make a contribution to the failure somehow, plus I got rid of one of the permanent CEL (P0037) I had.
Replaced front O2 sensor. Despite not giving any codes, neither been outside specs (2.16—2.90 ohms). I decided to change it being +100k miles old sensor.
Inspected and cleaned the Eccentric Shaft Sensor (ESS), not that it was dirty in the first place, but gave a try to this as well. Interestingly I discovered something else that may indicate an electrical/electronic issue. After installing the ESS, I haven’t been able to reset the NVRAM. I have done the 20 brake pedal procedure several times and I cannot get the dash oil pressure confirmation signal. I had no issues doing the procedure before with the RB Ren V1 flash, so I thought it may be a Ren V3 issue, spoke to RB again, furthermore sent the PCM one more time for further inspection and received feedback from RB that nothing is wrong with PCM neither with the flashing. Also, RB doesn’t recall having issues with any of their flashing affecting the NVRAM clearing procedure. But the fact remains that I cannot get confirmation that the NVRAM has been cleared or not.
Having no success with the electrical side, I went back to fuel, I inspected and cleaned the fuel injectors. Which were not in the best of shapes (See attached reports). I took the opportunity to inspect the UIM, vacuum hoses, blow air through the fuel lines, clean the throttle body, etc.
Currently, the car does feel a bit better. Yes, the injectors have made some difference, but the sluggishness remains and the AFR is still lean, plus the Commanded AFR and LTFT also remain stuck at the same values as before. I’m attaching the most recent logs I have produced.
I continue to believe this is an electrical/electronic issue, but I’m running out of logical ideas as to what else to do. I got a suggestion to remove the fuel pump pressure relief (PR) valve and go through an external pressure regulator, however, the discussions regarding the S2 pump in this forum indicate that this assembly is perfectly sufficient for an NA engine like mine. Plus the stuck AFR/LTFT logs are keeping me bias towards something affecting the PCM somehow.
Although fuel trims are not stored in the NVRAM, but in the KAM (which I have recently reset many times). I’m considering taking the car to the dealer to reset the NVRAM (if there is a way to do so through their scanner tool, rather than the 20 brake pedal procedure) to see if this could be somehow impacting the PCM (and the apparent stuck commanded AFR). Additionally, I’m thinking if I may need to re-flash the PCM back to stock again and see what happens.
Questions:
Does anyone has experienced inability to clear the ESS with the RB Ren V3 flash?
Does anyone has experienced inability to clear the ESS with the stock flashing (L calibration or later)?
Can the NVRAM be cleared without the 20 brake pedal procedure?
Could the main electrical harness be causing this? Did anyone experience issues with the main harness? What symptoms?
Thank you,
Piero
----------
Relevant mods in the car:
S2 Pump
Ported Engine (non-bridged)
Mazda C Coils / BHR Coils
RB Heater
BHR Resonated mid-pipe (Open cat)
Borla Cat-Back
Updated oil ventilation kit (Mazda)
Racing Beat+Revi intake
Racing Beat PCM Flash Ren V3
Sohn OMP adapter
93 Octane Gas
-----------------
I have been dealing with a lean condition for several months (no codes though). The WOT/Open Loop AFR (past +7k RPM ) is about 13-14, and the car feels sluggish. Last year AFR was about 12.4 on similar RPM’s. My car is an NA 2004 MT, and I mainly use it on the track. The engine was rebuilt early this year and it has about 1800 miles.
I have taken quite a few troubleshooting steps without success. The troubleshooting so far has been:
Inspected fuel pump pressure (S2 pump). The pressures fluctuate 52-58 depending on fuel tank level and temperature. However, I have not seen any sudden decrease in pressure that could be correlated with lack of fuel delivery. See post on: https://www.rx8club.com/series-ii-af...5/#post4823391. Additionally, I got hold of a Kenne Bell BAP and I installed with a manual switch. I can see 1-2 psi pressure increase while the booster is ON and the measured voltage getting to the pump is 17.5 volts.
Inspected for vacuum leaks. I did both a smoke test as well as carburetor spray around the intake manifold and injectors. I found a couple of small leaks, one at the UIM/LIM union and another at the MAF O-ring. Fixed both with no changes to the symptoms.
Replaced spark plugs and switch back/forth between OEM C coil and cables (~10k miles on them) and BHR coils and Moroso cables (~30k miles on the kit). I have also tested all coils with an HEI spark tester. I haven’t found anything wrong with neither of the kits, nor I have seen changes to the overall lean condition with one kit or the other.
Inspected, cleaned and also switched the MAF sensor with an original MAF from another 2004 car (+100k miles car). I have also logged data at idle and 2500 RPM as per Mazda MAF inspection instructions:
Mazda Specs: Engine speed Engine load calculated value (WDS PID: LOAD)Intake MAF (WDS PID: MAF)
Idle after warm-up (no load) 18.0—25.0% (LOAD) 3.8—4.7 g/s (MAF)
2,500 rpm 13.5—19.5% (LOAD) 8.7—11.7 g/s (MAF)
The attached data logged diverge from the quoted specs above, however, I noticed no difference between the two MAF sensors, which may indicate that this is normal with the Racing Beat/Revi intake rather than the stock intake? (Perhaps changes to the intake tube diameter?) The MAF at WOT shows +200g/s.
Looking at data logs at the time and the symptoms I was more inclined to expect an electrical/electronic failure. Reason being, the commanded AFR and the LTFT were (and still are) stuck at fixed values).
The AFR was Lean, yes, but the Commanded AFR was pretty much fix at 15.37 (both open/closed loop) with small dips to 14.65 (same goes to Lambda). It’s like the PCM does not want to change the AFR at all.
The Short Term Fuel Trim seems ok, fluctuating under 20%, however, the Long Term Fuel Trim is set at zero and does not change. I have done many logs, done many cycles with the car, run 20-30 miles expecting a change and nothing.
So with this in mind and having the Racing Beat (RB) Flash Ren V1 on the PCM, I opted to send the PCM for inspection to RB to check if something could have been wrong. RB didn’t find anything abnormal with the PCM and advised me that was better to flash the PCM with Ren V3 due to the ported engine, something that didn’t seem to be causing issues in the past, however, I gave it a try and flashed to V3, but this did nothing solving the issue.
Replaced rear O2 sensor. The sensor went bad ages ago since the lack of cat and had no resistance between the two connection terminals. I wasn’t expecting this to be the silver bullet, but I wanted to make sure this didn’t make a contribution to the failure somehow, plus I got rid of one of the permanent CEL (P0037) I had.
Replaced front O2 sensor. Despite not giving any codes, neither been outside specs (2.16—2.90 ohms). I decided to change it being +100k miles old sensor.
Inspected and cleaned the Eccentric Shaft Sensor (ESS), not that it was dirty in the first place, but gave a try to this as well. Interestingly I discovered something else that may indicate an electrical/electronic issue. After installing the ESS, I haven’t been able to reset the NVRAM. I have done the 20 brake pedal procedure several times and I cannot get the dash oil pressure confirmation signal. I had no issues doing the procedure before with the RB Ren V1 flash, so I thought it may be a Ren V3 issue, spoke to RB again, furthermore sent the PCM one more time for further inspection and received feedback from RB that nothing is wrong with PCM neither with the flashing. Also, RB doesn’t recall having issues with any of their flashing affecting the NVRAM clearing procedure. But the fact remains that I cannot get confirmation that the NVRAM has been cleared or not.
Having no success with the electrical side, I went back to fuel, I inspected and cleaned the fuel injectors. Which were not in the best of shapes (See attached reports). I took the opportunity to inspect the UIM, vacuum hoses, blow air through the fuel lines, clean the throttle body, etc.
Currently, the car does feel a bit better. Yes, the injectors have made some difference, but the sluggishness remains and the AFR is still lean, plus the Commanded AFR and LTFT also remain stuck at the same values as before. I’m attaching the most recent logs I have produced.
I continue to believe this is an electrical/electronic issue, but I’m running out of logical ideas as to what else to do. I got a suggestion to remove the fuel pump pressure relief (PR) valve and go through an external pressure regulator, however, the discussions regarding the S2 pump in this forum indicate that this assembly is perfectly sufficient for an NA engine like mine. Plus the stuck AFR/LTFT logs are keeping me bias towards something affecting the PCM somehow.
Although fuel trims are not stored in the NVRAM, but in the KAM (which I have recently reset many times). I’m considering taking the car to the dealer to reset the NVRAM (if there is a way to do so through their scanner tool, rather than the 20 brake pedal procedure) to see if this could be somehow impacting the PCM (and the apparent stuck commanded AFR). Additionally, I’m thinking if I may need to re-flash the PCM back to stock again and see what happens.
Questions:
Does anyone has experienced inability to clear the ESS with the RB Ren V3 flash?
Does anyone has experienced inability to clear the ESS with the stock flashing (L calibration or later)?
Can the NVRAM be cleared without the 20 brake pedal procedure?
Could the main electrical harness be causing this? Did anyone experience issues with the main harness? What symptoms?
Thank you,
Piero
----------
Relevant mods in the car:
S2 Pump
Ported Engine (non-bridged)
Mazda C Coils / BHR Coils
RB Heater
BHR Resonated mid-pipe (Open cat)
Borla Cat-Back
Updated oil ventilation kit (Mazda)
Racing Beat+Revi intake
Racing Beat PCM Flash Ren V3
Sohn OMP adapter
93 Octane Gas
11-16-2017, 03:42 PM
#3
Registered
Thread Starter
Join Date: Feb 2009
Posts: 13
Likes: 0
Received 0 Likes
on
0 Posts
I added the STFT channel to the previous MAF chart. Over that short interval, it went +/- (1-3%) while idle. Looking at other longer idle periods logs, it fluctuates +/- (8-10%)
11-17-2017, 01:22 PM
#4
Problem with this is that with the reflash we really don't know what RB altered in the maps
It almost appears that they have altered how the closed loop feedback is implemented. Having no LTFT seems almost too good to be true unless something is keeping them from setting. Especially with the pre-cleaned injectors . I would have expected that post cleaning things would changed.....
From my NA days I never really noticed much of a difference going from 12's at WOT to 13's..... so that even makes the slugishness even more difficult to understand. Problem with only one O2 sensor though is that you can rich in one and lean in the other rotor and have the O2 read normal
What do your plugs look like when you have pulled them after a good run?
It almost appears that they have altered how the closed loop feedback is implemented. Having no LTFT seems almost too good to be true unless something is keeping them from setting. Especially with the pre-cleaned injectors . I would have expected that post cleaning things would changed.....
From my NA days I never really noticed much of a difference going from 12's at WOT to 13's..... so that even makes the slugishness even more difficult to understand. Problem with only one O2 sensor though is that you can rich in one and lean in the other rotor and have the O2 read normal
What do your plugs look like when you have pulled them after a good run?
11-17-2017, 01:35 PM
#5
SARX Legend
iTrader: (46)
Well 8-10% is not good, I would think it's something in the flash, I have never seen any real results from an RB flash and who know what they are changing.
Last edited by 9krpmrx8; 11-17-2017 at 01:42 PM.
11-17-2017, 11:05 PM
#8
Registered
Thread Starter
Join Date: Feb 2009
Posts: 13
Likes: 0
Received 0 Likes
on
0 Posts
Now if I end up reflashing back to stock to test if this is what is causing the issue and considering what the dealership may charge me for the reflash, I’m thinking perhaps getting a Versatuner, mazdaEdit or similar license software and reflash myself. I will lose the RB flash regardless which way I go and will need to send it again to RB if I choose to use their flash again. The software would also give me the option for a custom tuning. Not that I would know how to do it, but could perhaps go through a local dyno and a remote or etuner…
Could it be something wrong with the PCM itself, and not the flashing?
RB feedback on the PCM and flashing was positive. I understand they verified the mapping against the one in the PCM. Then they reflashed again and mentioned that the PCM taking the flashing without producing an error was a sign of a healthy PCM.
11-17-2017, 11:06 PM
#9
Registered
Thread Starter
Join Date: Feb 2009
Posts: 13
Likes: 0
Received 0 Likes
on
0 Posts
Problem with this is that with the reflash we really don't know what RB altered in the maps
It almost appears that they have altered how the closed loop feedback is implemented. Having no LTFT seems almost too good to be true unless something is keeping them from setting. Especially with the pre-cleaned injectors . I would have expected that post cleaning things would changed.....
From my NA days I never really noticed much of a difference going from 12's at WOT to 13's..... so that even makes the slugishness even more difficult to understand. Problem with only one O2 sensor though is that you can rich in one and lean in the other rotor and have the O2 read normal
What do your plugs look like when you have pulled them after a good run?
It almost appears that they have altered how the closed loop feedback is implemented. Having no LTFT seems almost too good to be true unless something is keeping them from setting. Especially with the pre-cleaned injectors . I would have expected that post cleaning things would changed.....
From my NA days I never really noticed much of a difference going from 12's at WOT to 13's..... so that even makes the slugishness even more difficult to understand. Problem with only one O2 sensor though is that you can rich in one and lean in the other rotor and have the O2 read normal
What do your plugs look like when you have pulled them after a good run?
1. An old one from last year (2016) with somewhere between 8-10k miles (Didn’t labeled the rotors though). Before the rebuild Engine while using the RB Ren v1 flash.
2. The one I removed a few months ago, used before and after (2016-2017) the rebuild with the RB Ren V1. 3, may have 4k miles on them.
3. The current one, which I removed to do the comparison. No more than 1k miles on them. Used with the RB Ren v1 and now with v3.
Sparkplugs are not my strength, I replace them about every year after 6-8 track weekends. I haven’t really tracked the plugs usage well. Therefore, I will refrain from making an opinion. Will leave it up to you. Two things to highlight though, which may or not affect the plugs condition:
- I premix regularly with a light mix while on the road and a heavy one while at the track. This goes for all three sets of plugs.
- Since I installed the Kenne Bell BAP with the manual switch (maybe 200 miles ago), the pump doesn’t go through the fuel resistor. This tends to flood the engine. So far this has not been anything major than a couple of cranks without getting ignition to which I fully depress the gas pedal while cranking and the car starts promptly. This only applies to the last set of plugs.
