Car engine light is on and it has a slight miss in it. on 1999 Buick LeSabre

Sometimes misses when first starting until you push on accelerator and then it runs smoothly. Coils have been replaced and also spark plugs and wires have been replaced. Took to auto zone and PO304 was the diagnostic code that came up. Any ideas?

by in Pikeville, TN on July 10, 2011
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1 answer 1 comment
ANSWER by , July 10, 2011
Check the compression on the #4 cylinder and look for any vacuum leaks near that cylinder. I have seen a lot of cracked vacuum lines and leaking intake manifolds on GM V6s have these problems.
COMMENT by , July 10, 2011
Thanks so much for your help. Will have compression checked!