My wife had her 03 expo, fuel injectors cleaning service done on it and now a few weeks after you can hear a clicking sound. I used a long handle screw driver and put it on the top of the injectors and the sound is even louder. Any ideas?????

 

The injectors in these trucks have been known to be pretty loud. What motor do you have? I would also try posting in the V-8 engine area as you will likely get more of the motor buffs there.