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What does the fluctuating needle means in this vacuum test? Video uploaded to youtube

Motor Vehicle Maintenance & Repair Asked on January 15, 2021

I would appreciate any opinions on this vacuum test. Car is corolla 2001 1.8 engine with the code p0171. While the needle is in the normal green range, it fluctuates rapidly with very small movement. Engine has a very minor barley noticeable vibration while idling but runs fine. Please view the video i have uploaded Youtube video for the Vacuum test

Thank you!

One Answer

The fluctuation means a problem with a valve not seating properly or valve that is burned or warped. I can hear a valve tapping noise in your video (starts about 0:10 sec.). It's time for a compression check to confirm. I just did a vacuum test on my own engine. Here is the page from my shop manual that interprets the result of the test:

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Answered by Carguy on January 15, 2021

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