... after 254,000 miles! I don't think you can tell visually if they are "bad". Unless they are leaking -which could just be the O-rings.
Anyway, my car wasn't running too smooth at low rpms for the last 3-4 years. Swapped the heads and found one injector tip broken off. Bought a new "take-out" set (fiveomotorsport.com) and the difference is very evident off idle and low rpms. Runs MUCH smoother. Used to buck fairly easily also. I bet my mileage will go up.
Anyway, not sure if this answered your question or helped any... Mark
I don't know when that happened. It either broke when I took them out (during the head swap), or less likely, went through the motor. It was just a small piece of plastic - I didn't notice any performance change (if that's what happened.)
Any yes, if the lower is still on the car and a piece breaks, there is nothing to stop it from heading south towards the combustion chamber. But remember - my injectors were almost 17 years old - all the plastic is brittle. I don't think it's a big problem.
If you want to swap yours, just keep twisting and pulling on removal, making sure you don't bend them back and forth which may cause the bottom of the injector to hit the manifold (injector hole) and crack.