Engine Idle Shuddering?

2011 SUBARU OUTBACK

80,000 MILES • 4 CYL • AWD • AUTOMATIC

RRCHURLEY

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My car shudders while idling at stoplights or in traffic. Not every time and not too loudly, but enough shudder to make you feel it in your seat and see the hood move. Any ideas?

Feb 26, 2015 at 9:34 PM

HMAC300

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This happens when you have a leaky intake or exhaust valve or a vacuum leak, we should do a compression test to make sure the engine is in good shape and then do a vacuum leak test when the engine is cold only.

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

and

https://www.2carpros.com/articles/how-to-test-engine-compression

also when is the last time the engine had a tune up? If the compression is good and since you have the spark plugs out anyway I would install new ones. Please check the ignition coils for arching and replace those as well. Check out the images (below). Please upload pictures or videos in your response of the problem so we can see what's going on.

Images (Click to enlarge)

Feb 27, 2015 at 7:40 AM