My car starts to sputter when I get to about 45 to 50 mph?

there are 8 coils. retrieve the codes, there is most likely a Check Engine Light on, yes? trace down the codes and if needed replace the plugs, coils and boots if you don't have a vacuum leak causing the codes, which can happen. this is common on a direct ignition car ( yours is ) at about 90-100k

V6 (six) or V8 (eight)?....***You may need to clean fuel system due to all the build up of burning raw fuel prior to having the coils replaced) (thats was causes the misfire or sputter) to limit that sputtering A lot....or it may get rid of it if the coils are not the issue) **Try Gumout "ONLY GUMOUT" (complete fuel system cleaner ....yellow color) or for high mileage (orange color)... either works GREAT!$5 to $8.99 a bottle ..the other brands DON'T use!!! Autozone or Big parts stores carry it in the normal size...Wal-Mart mainly carry the new "2x" stronger smaller bottle for the same price now... ....****I use high oct gas and add half before filling tank and other half when about 50 mile to empty .......NO Sputtering now...but before (see below) ......I have a V8 and I had the sputtering really bad but I had that # 1 coil replaced and still was sputtering just not as bad but after about 100 miles engine came back on was now reading my #1 and #3 coils.....so I checked the coils and connection and found that the #1 coil (brand new) was defective ...(I determined that by putting one of the old coils in that #1 coil spot and had the engine light reset and bout 300 miles later the engine came back on then read #3 coil.. so checked the all the coils on that 1-4 side and found the coil connector (little black plastic piece)was not staying plugged and was not all the way on the coil connector, I also pressed it all the down on the spark plug... which prob happened when it was being installed.....and of course (ford dealer said they didn't do it) but my coil issues were on the driver side row of coils..........little easier to remove and check without the back screws on the coil housing cover...(note: I did not have the 2 screws put back on the end of the housing cover for the coils on the driver side (toward brake resvor) so I can check the coils, the connectors, spark plugs from time to time) ****Again........Also to limit or get poss get rid that sputtering A lot....try Gumout (complete fuel system cleaner ....yellow color) or for high mileage (orange color) either works GREAT! ....I use high oct gas and use half before filling tank and other half when about 50 mile to empty .......

I had the same exact problem with my 2004 LS V8...had to get all 8 coils replaced, runs perfectly now, no more sputtering.

I had to take my 3rd party intake breather off, put the original equipment back in and clean the Mass Air Flow Sensor with carborator cleaner, now it works like a champ. . . Go figure?

I have definately had this problem often. My car would change gears and shudder/vibrate/hesitate when excelling. It would knock my AC off for a few seconds but then everything would straighten out. Also, when ideling at a light my car would hesitate or shudder. There is a recall on the coil packs and the ford dealership will replace them free of charge. But the bad thing about it is, that they can't replace them all at one time. Once the engine light comes on,they will be able to put it on the machine and see what coil pack it is. They will then replace the defective coil pack and spark plug. I have had this problem for 2 years but I have had no problem in getting them fixed. They are under recall so it is free to you. I hope this helps.