Answer for question: "When you really need to start worry about your fuel trims or misfire?"

Prozento

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Hello CivicX community

I decided to make a thread about an official normal values for K.count/misfire and fuel trims that I found in Honda service books for our model. Take this info as an answer for when you really need to worry and when its just something you need to keep your eye on. Hope it will help for someone here.
__________________________________________________________________________________________
Fuel trim - too high:
Malfunction Threshold: Long term fuel trim is higher than 1.32 (+32 %) / 1.33 (+33 %) - 1.5 / 2.0 Engines

Fuel trim - too low:
Malfunction Threshold: Long term fuel trim is 0.79 (-21 %) or less.

Possible Cause:
Fuel pump failure
Injector failure
Fuel pressure regulator failure
Fuel line failure
Fuel supply system failure
Mass airflow (MAF) sensor range/performance problem
Manifold absolute pressure (MAP) sensor range/performance problem
A/F sensor (sensor 1) failure
Secondary HO2S (sensor 2) failure
Vacuum hose misinstalled
Throttle body air leak
Intake manifold air leak
EVAP canister purge valve failure

NOTE: The causes shown may not be a complete list of all potential problems, and it is possible that there may be other causes.
____________________________________________________________________________________________
Random Misfire; No. 1/2/3/4 Cylinder Misfire:
Malfunction Threshold: The number of misfires versus engine revolutions is equal to or greater than these values
1. Misfire Type 1 (Severe) - Per 200 revolutions 17 - 89 times (Depending on engine speed and load).
2. Misfire Type 2 (Light) Per 1,000 revolutions 77 times

Possible Cause:
Ignition system failure
Fuel supply system failure
Intake air system failure

NOTE: The causes shown may not be a complete list of all potential problems, and it is possible that there may be other causes.

____________________________________________________________________________________________
So these are the official values. Hope now we will be more relaxed when our fuel trims inside the city jump to -10% or when 5 misfires happen after 2 hours of driving.

P.S.
Another good threads:
Fuel trims
https://www.27won.com/blog/yeah-but-what-are-your-fuel-trims
Misfire
https://www.civicx.com/threads/what-is-knock-count-and-knock-control-defined.38412/
Knock control Ktuner files
http://www.ktuner.com/KTunerHelp/ignition_timing_and_knock_control.htm
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PowerPerLiter

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Yep! Nice post.

It's a funny thing the misfire/k count stuff.

In almost 30,000 miles of driving and countless flashes I can maybe say the car showed 10 "misfires".......ever......

Even when my injectors were failing to the point of limp mode and almost not even making it under its own power to the dealer to trade it in.....not a single registered misfire.

Maybe I just had one of the better running cars or the fact I always ran premium. I dunno. It took me quite a while (and I still have a hard time believing based on my experience) to accept that "misfires" are "normal" for these cars.

Especially the folks that show 20-40+ in one drive cycle.

I nearly had to TRY to get k.count to move (i didnt want it to obviously but my 2018 was laughably "knock resistant")


To be clear I am by no means contesting this information as this is an excellent post with factual information.

Thanks for sharing!
 

NoKz

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Nice post, thanks.
 

arnoldo

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Honda does not activate Fuel Trim reading in South East Asia Civic 1.5T CVT ECU. This confirmed by both KTuner and Hondata. In this case, is there anyway to assess through Short Term Fuel Trim?

Sorry, could anyone please help me to understand what does Per 1,000 or per 200 revolutions means in layman term?
 
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Prozento

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Honda does not activate Fuel Trim reading in South East Asia Civic 1.5T CVT ECU. This confirmed by both KTuner and Hondata. In this case, is there anyway to assess through Short Term Fuel Trim?

Sorry, could anyone please help me to understand what does Per 1,000 or per 200 revolutions means in layman term?

There is nothing about short term fuel trim. About how to get to the long one - I am really a newbie so better wait to other pals, but if you have Ktuner you can try make the following steps:
1. Record a long datalog using your Ktuner unit
2. Open the datalog in the Ktuner software
3. While the datalog is opened use "export to CSV" option in "Tuning" window (upper left side of the software.
4. Open this new file with Excel
5. Find the short trim readings in the file
6. Point all the column and use "Average" tool in Excel.
Try this and see what it gives you. Hope it will help

Edit: if you want to see real numbers don`t include "zero" values in the average tool.

About the revolutions:
Your engine RPM is revolutions per minute
So if you were cruising in 110 kmh for 1 minute, and your engine made close to 2500-2600 revolutions for this period of time. Thus, if for type 2 misfire problem you need to get more than 77 misfires, you should get like 180 misfires for this period of time. Same with type 1 just use other numbers. The error light will come before of course but this is just example for an easy explanation.
 
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arnoldo

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There is nothing about short term fuel trim. About how to get to the long one - I am really a newbie so better wait to other pals, but if you have Ktuner you can try make the following steps:
1. Record a long datalog using your Ktuner unit
2. Open the datalog in the Ktuner software
3. While the datalog is opened use "export to CSV" option in "Tuning" window (upper left side of the software.
4. Open this new file with Excel
5. Find the short trim readings in the file
6. Point all the column and use "Average" tool in Excel.
Try this and see what it gives you. Hope it will help

Edit: if you want to see real numbers don`t include "zero" values in the average tool.

About the revolutions:
Your engine RPM is revolutions per minute
So if you were cruising in 110 kmh for 1 minute, and your engine made close to 2500-2600 revolutions for this period of time. Thus, if for type 2 misfire problem you need to get more than 77 misfires, you should get like 180 misfires for this period of time. Same with type 1 just use other numbers. The error light will come before of course but this is just example for an easy explanation.
Thank you for the explanation in regards to revolutions.

I am using Hondata Flashpro. Both Hondata and KTuner confirms that LTFT reading in South East Asia ECU is not available and always show 100%. Both companies suggest to pay attention to STFT instead.
 
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Prozento

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Thank you for the explanation in regards to revolutions.

I am using Hondata Flashpro. Both Hondata and KTuner confirms that LTFT reading in South East Asia ECU is not available and always show 100%. Both companies suggest to pay attention to STFT instead.
I am almost sure Hondata has the same "Export CSV" file option. When I have checked my STFT readings without the 0 values I have got 6.3 average while my LTFT is 7.8 average. Yes, they are not the same but it can give you some data about your LTFT.
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