LTFT figure stuck at 0 and Bad fuel economy? 2013 Nissan Rogue
I recently bought my 2013 Nissan Rogue used and have just realized that it does not produce any Long Term Fuel Trim data for my scan tool. When I use my scan tool to read for LTFT it's always 0. It does produce Short Term Fuel Trim data. I have already tried resetting ECU and been driving the car for more than 100 miles since the reset, but still no sign of LTFT data.
Potentially connected to this is the fact that my car has very bad fuel economy. I have read somewhere that LTFT stuck at 0 may have to do with EVAP problems (somewhere a sensor is not sending signal to the ECU), which can cause bad mileage because a bad EVAP valve can have the effect of a vacuum leak (air-fuel mixture gets vented outside instead of being routed back to the combustion chamber, thus creating a lean condition).
My A/F wideband oxygen sensor does report frequent lean spikes once RPM goes above 1500.
Anyone has any idea as to what the meaning of all this is? I'd appreciate greatly any input from you. Thank you!
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Also, are you using obd, or vehicle specific parameters when looking at pids??
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I use BlueDriver. I believe the parameters used are OBD.
I am attaching a combo chart of my STFT and RPM readouts. The blue line is STFT. As you can see, there are very frequent 25% lean spikes. The orange line is RPM. It seems that the lean spikes occur when RPM climbs above 1500. I don't know if there is a real causal relationship behind this seeming correlation.
https://imgur.com/a/6UxOia2
Since I bought my car I have done the following maintenance work:
1) Engine oil + filter change
2) Air filter change
3) MAF cleaning
4) Spark plugs change / Coils checked (all good)
5) CVT fluid change
None has helped my fuel economy.
I have not carried out a vacuum check as I have read at several places online that vacuum leaks tend to have its greatest effect at idle (and that their effect reduce as RPM goes up), but my lean spikes seem to occur only when RPM and vehicle speed increase.
So I am now inclined to think that my bad fuel economy originated from either a EVAP or a fuel-supply-side issue - something that kicks in once RPM rises to a certain level.
I am only a novice DIYer so I'd appreciate some guidance. Thanks.
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But my STFT + RPM and SRFT + Vehicle Speed (km/hr) are here:
imgur.com/a/irFu7Ux
Thanks
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It is very possible the Bluedriver is not picking up the LTFT. If you are using the latest firmware, try rolling back version by version until the LTFT shows up. IF, you have access to another scanner, try it to compare.
Also, before you try rolling back, try it on another vehicle to see if the LTFT is there. After every update/rollback reset the apps data/storage.
As good as the BD is for global OBD it sometimes has a few caveats. I have seen a few new firmware updates that were not good and BD support said to roll back until they figured it out, which was rather quickly.
Paul
Never stop Learning.
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How about an A/F sensor b1 pid? Looking for 2.2v with close fluctuation to that number. Can you force that number to go up by pulling a vacuum line? You should be able to make the alpha go up the same way. Stuck at 2.2v could mean a sensor problem.
Nissan Technician
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The AF sensor does have a readout, and the figures do tend towards 2.2 volts (but they do not get stuck there), with sharp lean spikes (all the way to above 4.5 volts) that correspond with the positive STFT spikes. Please see the following chart.
imgur.com/a/kswaPBX
I will have to ask around before I can find another car to try my BlueDriver on.
I have also posted my MAF and RPM chart at the link above. It seems that MAF and RPM do correlate with each other, though I can't tell whether the correlation is as proportionate as it should be.
Thank you.
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Voltage when it comes to A/F sensors and scantool values are an interpreted value by the scantool. The stoichiometric ratio of 14.7.1 in voltage for Nissan is 1.47v and changes in value are measured in current not volts but the scantool will show that interpreted voltage value.
Can you post a graph of RPM, STFT and LTFT at idle then increase RPM to 1500 then 2500. Please do not overlay the data.
"an open mind let's knowledge flow in and wisdom flow out for a man who has neither never listens to those who have both".
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As for the stoichiometric voltage for the B1S1 wideband oxygen Sensor, according to my service manual, as Tutti57 pointed out, it is 2.2 volts. But I am a novice so maybe I am confused about the whole current-voltage thing.
Thank you
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In any case, I will get you some charts of my car at idle tomorrow.
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I recorded the 2.2v in my records so I will confirm and update...
"an open mind let's knowledge flow in and wisdom flow out for a man who has neither never listens to those who have both".
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Nissan Technician
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In any case, the lambda readout correspond with the AF sensor readout with all its lean spikes.
I have added the lambda chart to the bottom of the same link:
imgur.com/a/kswaPBX
I will get some at-idle charts tomorrow. Night-night.
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"an open mind let's knowledge flow in and wisdom flow out for a man who has neither never listens to those who have both".
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Nissan Technician
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And I don't have the idle charts to show you yet. I examined the PCV valve today and found the stopper inside to be not rattling freely as it should. I have installed a new one and have yet to test drive the car to see if it makes any difference.
I'll see if I can do the idle rev tomorrow.
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Nissan is also kinda weird about Long Term trims. :silly: So I'm not surprised at all that your Long Term PIDs show zero.
What's the average fuel economy that you're seeing? :huh: Highway, city driving?
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