I don't see a particular issue with it. Those are pretty normal values. Your scanner is misleading you somewhat, Kia does not have LTFT STFT per say, they have Idle, and partial load trims so not sure which trims your data is interpreting as which but it is misguiding you a little. If I get a chance to today I will take a snapshot for you of what it looks like on a factory scanner. You want to look at the Lambda values more, only time it goes haywire on your chart is when you step off the gas after accelerating and that is perfectly normal. It is a lot easier to read these if your scanner will allow you to graph them rather than to chart the numbers. You might want to mention which engine and transmission you have also.

 

Its Kia Soul 2016 1.6L (base model) automatic.
You mentioned Lambda values - What is the range of good Lambda values ?
If you can direct me which columns have most useful information I will create charts, I Just dont have a good idea which columns I should look at.
Thank you for your useful remarks !.

 

First question, are you actually having issues, or did you just randomly look at some data and convince yourself that you are?

 

That's a good question, Ill have to go to more details to answer that.

1. It began at 2019 when I noticed that fuel consumption increase, It wend up from about 28 MPG to about 22 MPG, the OBD showed dramatic lean condition - Long tunf fuel trim is ~25% when engine runs in idle.
2. The dealership scanner showed engine error codes and they found a problem in the injectors - clogged injectors. they replaced it under warranty. everything went back to normal and I scanned LTFT to be under 5%.
3. After a about a year I noticed again that fuel consumption went up, scanned the LTFT to be about 12%
4. The dealership checked the car and this time they say they dont see any problems, so they did nothing.
5. Since then fuel consumption improved again to 28 MPG but the LTFT values increased a bit to about 15-17% on idle. I tried to use injector cleaners (saw a youtube by Scotty Kilmer recommended that) It didnt change anything.
6. Last year I noticed a new noise appear at 1500-1600 rpm, when I slowly accelerate. Its like a soft noise of knoking from the engine. Other than that everything looks and sound normal.

I will add the diagnosis results of the dealership for both time the car was there.

During this whole saga I never saw the check engine lights turned on or any engine error codes in the OBD scanner.
AFAIK lean engine for a long time can damage other components in the car such as the catalytic converter, So if there is a problem I want to solve it as soon as possible.

 

Your case sounds rather rare. For starters I have seen maybe a handful of injectors fail on Kias period and that's GDI and MPI engines and never replaced all 4 on one car, have done 2 at once but one would be worse than the other and was probably a problem before the 2nd failure that made the car really act up. The tech who wrote the diagnosis sounds pretty competent and stated all relevant items to your car so there had to be sound reason to believe all 4 injectors failed I just have never seen it on a Kia or any other car for that matter where all injectors failed unless some kind of fuel contamination came to play here. It would be like saying all 4 of your coils burned out at the same time, it just doesn't happen because the probabilities of that are somewhere better than a lotto ticket.
On the Kia factory scanner (KDS he refers to on your paperwork) you will see idle and part load fuel trims and Lambda values as well as watch the upstream A/F sensor. I usually take a test drive with the parameters I want to see in graph mode and I can stop it and replay it at any time if I see a spike in the graph. The Lambda correction value should be at 1.00, any variance from that is your fuel trim adjusting rich or lean and that is normal unless it goes haywire during idle or steady driving or even steady acceleration. I'll try to take a 2nd look at your data but it is hard to scroll around on it. About the only data points I would want to see to start with (for the issue you are describing) would be: fuel pressure actual and requested side by side, O2 bank1 sensor 1 (it is an Air Fuel sensor but they still call them O2s) on the Soul you should see something like 1.48-1.5 volts with a fluctuation any time you floor it or get off the gas, accelerator position % (not throttle position, the TB goes full open even during mild acceleration) and the Lambda values along with RPM. I wonder if you have a MAP sensor issue or there is a potential small vacuum leak. Perhaps it would be best to check out the MAP and do a quick smoke test on the intake. This might take some deeper digging, it could be even mechanical like cam timing acting up but not for long enough to throw a code or even the stupid purge valve that is failing but not enough to throw a code.
Maybe this will help, pictures attached

 

Wow, thank you so much for digging dip into it and for the detailed advises.
I'm sorry about the data format being hard to read, I have it on Excel page but the forum system is very limiting in the file types it allows to upload.

Few question I have :
1. The Long Turn Fuel values which goes up to 17%, isn't that a big issue ? what value will trigger an Error or Engine check light in the Soul ?
2. I noticed that the fuel rail pressure is thousands of PSI ... is it normal ?
3. In the first diagnosis the dealership mention "Ignition Timing" retarding, Is it the "SPARKADV" my scanner show ? and if so, are the value I measure in range ?

BTW, I replaces the Purge valve couple of years ago when there was a suspect it might cause the problem, I'll check it again.
And I just remembered that in a later phone call with Kia Usa they mentioned that they see that dealership did replaced 2 injectors. so Im not so sure they did replace all 4.

I created the graphs with the fields you suggested, I added a big chart that contain all the fields after I normalized the values to make it fit in one chart.
I also attached the raw text file created by the scanner contains freeze frames of data. Just in case it might help.

Again thank you so much for the useful information !

 

What is the mileage on the car?

Also, what is your oil change frequency & do you use an OEM filter or 3rd party brand?

Was curious too on your MPG take. Fuel economy usually goes down in winter months, from extra idling & engine strain etc + winter blend fuel. I've tracked mine for 8 years and same pattern, fuel economy will drop up to 4 mpg.

 

Here’s the same notice Geo just posted, but a little easier to view

https://static.nhtsa.gov/odi/tsbs/2020/MC-10177729-0001.pdf

 

Thank you all for this new information, since I'm going to start change the oil myself, It will be easier for me to do it more frequent, as Kia recommends.

 

@benoved,

Curious. What scanner and software are you using? What country did you come from?

With the kind of driving you are doing, you should think about cleaning the back of your intake valves. Yours is a GDI engine and requires extra maintenance.

 

@benoved,

Curious. What scanner and software are you using? What country did you come from?

With the kind of driving you are doing, you should think about cleaning the back of your intake valves. Yours is a GDI engine and requires extra maintenance.

I'm using Autel 519 scanner, and the software is a code I wrote in Python + Jupyter Notebook - had to use my software engineering experience to work with the raw data this cheap scanner produces (the horrible text file I attached in earlier reply message). I came from Israel.

I will look for video guides for intake valves cleaning, thank you !

 

This may sound crazy but... You said you drive the car with very light throttle all the time. Have you tried a few hard runs to redline? Aka a Italian tuneup??

 

Yes !, one mechanic I used to go to told me that running the engine 3000-4000 from time to time, is important to the engine and system health. since I don't have many long rides out of my city, I'm locking the transmition in low gear (3) and driving slowly in the neighborhood around while making alot of noise . I try to do it at least once a week or two.

 

Looks to be coming off throttle trims shoot high not uncommon. Dirty throttle body or Injector pintle could be slow to close. Could be a variety of issues tough to tell without getting the hands on the car.

 

What puzzle me is that never even once the check engine light did not light even when I had the LTFT around 25%. How high those value should come to turn on an engine error ?

 

Just a DIYer but I thought 20% was the threshold but someone probably can find the exact number of cycles and longevity to set it.

 

Only fuel pressure you will see is the pressure in the high pressure rail, you will not see the low pressure fuel pump numbers. There is a desired and actual, if they are close the pressure is good. You should see around 500ish psi at idle and 2k psi under high load on the high pressure side.

 

I looked at the charts, and it does behave like you described. at least the max fuel pressure. Ill try to scan again with more advanced scanner.

 

On some models I can see both pressures, low and high. This is from a 2017 Sportage

 

Does it sputter at all. That lambda near 2 is insanely lean. That can’t be correct. Other than that everything looks relatively normal to me but I am no mechanic. Can you pull the down stream sensor? Might be in mV.

 

I added both O2 sensors, and a chars contains few parameters values normalizes on the same axles just to make it easier to see the relations between the parameter and maybe help to get an intuition.

 

That has to be the upstream voltage switching that quickly. I’m with the mechanic I think it mostly looks normal. Running a tad lean but not out of norm. I don’t see anything major average LTFT still under 10 combined also under 10. That lambda value near 2 isn’t correct. Car would stall. I would double check your mileage again sameish driving conditions. More post Covid traffic in your area?

 

The problem with the LTFT is a high value when idle. at about 500 rpm it goes 15%-19%. when driving it does go way down. thers no real change in the traffic between pre and post covid in my area.
I just did oil exchange and fuel additive which should clean the injectors. I will take new driving data soon and update this post.
Thank you !

 

EVAP purge stuck open would set a code. EGR and IAT likely too. Have you ever disconnected the battery to reset the fuel trims?

 

When I replaced the battery about a year ago. It didnt change anything. Maybe I should try this again ?

 

If you disconnect it will reset the keep alive memory which stores the fuel trim data. Worth a shot before digging into everything else. Evap data, EGR data, IAT and mass air flow rates to check the maf

 

Any luck with the battery disconnect? Other options minor vacuum leak on intake or elsewhere, dirty maf, fuel delivery, or o2 sensor or exhaust leak pre cat. Vacuum probably most likely

 

I will have to find enough time to do it properly. I want to drive a specific rout before I reset it, and after to make a correct comparison. Will have to find enough time to it soon.

 

Update and happy ending.
3 years after I solved the Issue.
The LTFT got to a all time high of more than 30%, no check engine light. rough idle, and high fuel consumption around 24-25 in the city.
After watching a youtube video of how to pull out the injectors clean them and put it back,I did it, it was a long process, the injectors head was black, carbonized, I clean it with carb clreaner, and after that - ultrasonic cleaner using only hot water with dish soap.
after putting it all back, the car runs like new. Idle is smooth, LTFT back to 3%-4%, and fuel consumption is amazing, in the city im getting 32-33 mpg.
The car have 80k miles, last time they replaced the injectors was at 40k miles. looks like every 40k it should be part of the service.