Fuel injector or coil?

[Locknut]

Had four injectors replaced over the last three years on my 91 and now the car is starting to run a little rough again. Could it be a coil? How would you know if it was a coil and not an injector? Does the coil just go dead and you lose power on that cylinder...or does it act up like the injector until it finally goes. Sorry if this seems a little lame, but I just don't want to believe I have to replace another injector.

[Q45tech]

If 1 fails it might be a fluke, 4 failures means all of them were critically exposed to defective gasoline.

[3rd Q]

Lock,Oh the joys of Q fuel injectors in the Midwest. If you feel the familiar symptoms, you can bet it's the injector, not the coil. See q45.org for an easy way to ohm them through the harness- so you don't pull the plenum needlessly- it might be one of the 3 easy to get to ones.

BTW, I've replaced 31 injectors over 10 years between 3 Qs, so your experience, unfortunately, is not unique.

Paul