I have an 01 s-type v6 with random rough running condition. At any speed it runs flawlessly but as soon as you come to a stop it starts to idle slightly rough. It is not severe enough to die and will not set any codes. I have replaced all the coils and plugs as the valve cover gaskets were leaking and fouling out the coils. Fuel pressure is steady and well within specifications, ran 2 cans of bg fuel system cleaner through it and still have the same problem. No vacuum leaks, oil separator gaskets are good and sealed, intake gaskets good. Will not show change when introduced to parts cleaner or propane and sensors all show proper readings using datalogger.
any suggestions?

Thanks, Nick

 

I'm not a tech, but it sounds to me like you may have a bad injector.. Do you have any software that has a miss counter that you could use to see which cylinder/s is causing the rough idle?

 

What kind of coils did you put in?

 

Everything is from the dealer, factory replacements. All computer information using IDS shows nothing funky and still shows no misfire. Even using the misfire monitor doesnt show any counts at all. All software has been updated.