after starting vehicle it idled very rough and then stalled. Restarted and found it to be skipping and knocking. Brought it into the garage and pulled spark plugs. Did a compression test and found that #3 cylinder has zero compression. The mechanic has a feeling that it may be the valve seat or the valve face has broken off. please respond with any info that will be helpful. Also wondering if there may be a recall on the valve train?