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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 !
Thanks. Am currently looking for a scanner that will read a Kia Soul as well as a Nissan Xterra.

Yes, Israel should be hot enough.

This document covers intake valve cleaning and might be helpful:

How to prevent oil and power loss in a Kia Soul GDI engine
 
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Discussion Starter · #22 ·
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.
 

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Discussion Starter · #24 ·
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 ?
 

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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.
May seem dumb but you don't happen to fill your tank till it's at the top of the neck do you? One of the issues caused by doing this is poor fuel millage as the vapor recovery system get clogged and the computer cant regulate correctly, also the vapors sent into the system tend to assist in economy . If the fuel tank does not correctly pressurize your injectors cant work right either. Has the fuel rail been checked for fuel pressure as well? a weakening fuel pump wont send a code either till it's seriously bad.
 

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Discussion Starter · #27 ·
May seem dumb but you don't happen to fill your tank till it's at the top of the neck do you? One of the issues caused by doing this is poor fuel millage as the vapor recovery system get clogged and the computer cant regulate correctly, also the vapors sent into the system tend to assist in economy . If the fuel tank does not correctly pressurize your injectors cant work right either. Has the fuel rail been checked for fuel pressure as well? a weakening fuel pump wont send a code either till it's seriously bad.
When the pump stops thats it, I dont try to fill any more. But you gave me a new direction to think about. Maybe the problem relates to vapor system ? The fuel pressure is showing in the OBD data, I just dont have the experience to understand if the values it shows are in the norm range.
 

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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.
 

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Discussion Starter · #29 ·
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.

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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.
 

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Discussion Starter · #32 ·
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.

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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?
 

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Discussion Starter · #34 ·
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 !
 

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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 !
no problem to be honest not sure I will be able to tell. What is your idle RPM. When you come off on the chart above it looks ok. Usually around 700ish. If it were a vacuum leaks or EGR valve stuck open it would read higher. Other would be dirty maf not reading air or IAT. You can see how this can be one of many issues and you would need to test them to eliminate them. A shop could also potentially confirm the lean condition with a gas analyzer but that is old school.
 

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Discussion Starter · #36 ·
no problem to be honest not sure I will be able to tell. What is your idle RPM. When you come off on the chart above it looks ok. Usually around 700ish. If it were a vacuum leaks or EGR valve stuck open it would read higher. Other would be dirty maf not reading air or IAT. You can see how this can be one of many issues and you would need to test them to eliminate them. A shop could also potentially confirm the lean condition with a gas analyzer but that is old school.
The RPM at idle is around 500-600.
I tried to clean the MAF myself - did not made any change.
It was checked at the dealership about 6 months ago, then I had also bad fuel consumption which got much better since then (I used injectors cleaner fuel additive but im not sure if that was the reason for the improvement ?)
but since then the LTFT value at idle has gone a bit higher.


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