Tachometer hand "dancing"

2017 NISSAN ALTIMA
13,800 MILES • 2.5L • 4 CYL • 2WD • AUTOMATIC
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WPOORE94
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Just a quick question, I bought this car about a week ago and it is running and driving fine but the tachometer hand seems to bounce just a little when coasting or going at a steady speed. It does not do it while at idle or when speeding up. What could be causing this?
May 5, 2018 at 6:40 AM
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STRAILER
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Hello,

When this happens it usually means the ignition system is back feeding into the electrical system caused by a bad ignition coil or spark plug (common.) I see the car is fairly new which makes me think a spark plug was cracked from the factory or just a bad coil.

Please remove the plugs and coils to inspect for burn marks (black tracer) which means you have found the problem.

https://www.2carpros.com/articles/how-to-test-an-ignition-system

and

https://www.2carpros.com/articles/how-to-change-spark-plugs

Please run this test and get back to us.

Cheers, Ken
May 6, 2018 at 5:25 PM