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post #1 of 5 (permalink) Old 03-29-2016, 01:37 PM Thread Starter
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Low Compression

I have a 2009 Cobalt SD with 55000 miles. It is running very rough and knocking. Mechanic says compression is only at 50 (instead of 150) in two cylinders...and only fix is a new motor. Could this be caused by anything else?
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post #2 of 5 (permalink) Old 03-29-2016, 02:33 PM
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Piston rings, valve seals, or head gasket. Would need a leak down test to know what is for sure the cause.

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post #3 of 5 (permalink) Old 03-29-2016, 04:19 PM
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A one tooth timing chain jump would do these very symptom. Rough idle, knocking and very low power.

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post #4 of 5 (permalink) Old 03-29-2016, 04:52 PM
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That would cause low compression on just 2 cylinders? I would think that would be all 4

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post #5 of 5 (permalink) Old 03-29-2016, 05:12 PM
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Nope just 2 and it would be the other if it jumped the other way. 1-4 or 2-3, this is if it jumped at the crank if only one cam jumped different symptoms again.

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Last edited by Coby7; 03-29-2016 at 05:14 PM.
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