Use ENGINE FUEL TRIMS to confirm vacuum leak

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#diymechanic #obd2scanner #cardiagnostic

[joesitter]

Thank you for your very clear, helpful and easy to understand explanation.

[EverydayProjects]

Really Good explanation using the graph.The short term fuel trim reacts to a change .The Long term fuel trim adjusts to the new mixture then the short term returns to 0 until there is another change. I get this now. Thank You! You used the word "SCOUT" and that made sense to me. The short term fuel trim is the "SCOUT" that goes ahead when there is a change such as a vacuum leak. Once the Long Term adjusts to the new conditions, the short term returns to 0, ready to monitor and change for new conditions.

[charleswilson]

Great video! I've explained my situation to many mechanics and none of them could figure out what my problem is. You just told me what my problem is with this video, and now I can use my smoke machine to find the leak and plug it before anything worse happens. Thanks a million!

[SerMajorEcho]

Such a clear and concise video 💯great work

[Autofixgarage-ng]

Perfectly explained. Pls we need video on bad maf sensor response on fuel trim

[michaelethangross]

Does it matter if you step on the gas while the vehicle is in park or neutral and the fuel trims decrease vs. when driving in gear i.e. could a fuel delivery problem likely be more exposed under load or would a fuel problem even show when increasing rpms in neutral? In other words, the STFT going into the 30s when accelerating would indicate a fuel problem, of course you could have both a vacuum leak and a fuel problem at the same time.

[backendninja]

Best videos ever on fuel trim. Can you explain now negative fuel trim?

[sammahasona]

Amazing video. The best I have seen. Thank you very much!!!!

[billybanter]

I ahve a misfire in ylinder 1 would that affect fuel trims?

[mydiy]

Need help regarding SAE J 1962 protocol compatible scanner and apk too.thanks

[chrisisho]

What mean if I have Zero short term and 27% long term, i have P0086& P0106,
No vacuum leak at all
Any suggestions to solve this issue,
My other question for you, when try to find vacuum leak the some should goes out of Oil cap when open it or no ?

[cosmicure-truthinshort]

Thanks for your video. On my 2004 1.6 VW polo i have code P1128 Long term fuel trim bank system too lean. Car is using a lot more fuel. When engine is revved fuel trims climb. Driving on long downhills with foot off throttle fuel trims drop. Can't find any vacuum leaks. Is it possible that fuel pump is not giving enough pressure? MAP sensor is still quite new and readings seem to be fine. ECT readings fluctuate between 78 degrees Celsius on open road to around 84 degrees Celsius in traffic. Any advice would be appreciated