I believe Tonyroy1 is on to something! My daughter's Taurus would spit n sputter from start, put it in gear and you better give it gas, engine hot or cold didn't matter! Usually it's the #4 plug that won't be getting spark, pull the #4 wire while holding a screwdriver close to the tower on the ign module, if that plug is firing the spark will try hitting the screwdriver before it hits you. Make certain to get the exact module for your engine, diff modules do have diff firing orders, and remember if ya go for a $20 unit that's all it'll give ya, $20 worth then you're walking! (learnt that the hard way) A steady misfire will act n sound exactly like a vacuum leak! Also check the connections of all the injectors, and check fuel pressure.