1988 240 DL N/A with 284k+ on a broken odometer.

My car's been idling a bit rough 3/10 in intensity since I've gotten it. I've changed the entire ignition system and used fuel injection cleaner in an almost empty gas tank. Nothing helped.

My mileage has been shotty; I suspect a leaking o-ring in my fuel injectors is the culprit (the car is the queen of deferred maintenance).

I've never done this on any car I've owned, but after watching YouTube videos, I just removed the fuel injectors and cleaned them with carburetor cleaner, each injector three times. Their resistance was normal, I heard clicking when I applied voltage to them, and each of the three spray patterns for each fuel injector were conical, so I *thought* that I was wasting my time. However, immediately upon start up, the car idled almost perfectly smoothly for the first time and did so when I idled it later. I was shocked and impressed.

By the way, #1 and #2 o-rings were firm, #3 and #4 soft. I replaced all o-rings.

Removing and reinstalling the fuel injectors and putting on new o-rings is not my favorite task, but I'm going to start doing this regularly. The question is how often.

I checked the brickboard FAQs, but there's no discussion as to how often to do this off-car. Any suggestions?