Do fuel injectors go bad? I can see a physical difference between the 4 I took off, looking down the top there are 3 prongs that look like they might be sensors. One injector has all three really prominantwhile the others are in various states of wear.
I have an 89 Volvo 240 and they have never been replaced.

 

You could have them cleaned and flow matched. The machine tests them as well and would tell you if any were bad. They could just be dirty or worn. I have a friend with such a machine and he did mine for free. It's around 15-20 bucks per injector around these parts to have that done.

And to answer your question: Yes, injectors do go bad.