307 hdi 1.6 2005 Misfire

friends, I haven't been with you for a long time. hello again everyone ... masters i know i have 206 gti car recently i have been facing a problem like this, i'm running the car there is no problem but the engine sound of the car changes when it is cruising (the boat starts to sound like a water engine) and the car starts to sing, search for it doing it, sometimes stopping while in rolentide. why is this caused? I think it may be due to an ignition system or injections, but can more experienced friends help me? Thanks & nbsp;

I can do the coils from the coils or the spark plugs.

[QUOTE = lew40] I can make it from the coils or the spark plugs my friend look at the tool on a pc.