2003 Chevrolet Impala 3.4L with the engine code p0300

Question

I have a 2003 Chevrolet Impala 3.4L its misfiring I change coils got new spark plugs I even got a tune-up its fine once I get to high speeds but anything below 30 it misfires pretty bad

Answer 1

P0300 Random misfire

The mechanical condition has to be ruled out, such as burnt valve, low compression,

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Here a cylinder leak down was performed, on a suspected cylinder, after a cylinder head was removed, what was found was a crack between the intake valve and exhaust valve, this condition set a P0300. and a cylinder head repair was the fix.