Hi,
I have a 2006 GT nothing fancy minor mods. Three days ago I did a routine oil change. Now I have what sounds like a ticking lifter. It started approx 20 miles after the oil change. I bought another Filter and changed the oil a second time about no changes. Now when I come to a stop the car is idling very rough.

It sounds like a valve might sticking if you rev the car up til about 3500 rpm at 4000 it will start idling normal again still ticking though. Get to around 60 mph and slow down it idles rough again. Does anyone have any idea as to what it could be? I am not a mech.

 

Sounds like you should do some research on the net to get suggestions on what it could be. I don't know if it has hydraulic lifters but I would suspect that if the engine has them. One could get fatigued and collapse leaving too much clearance and make a ticking noise. I haven't taken a Ford 4valve head apart, maybe someone who has will jump in here.