I replaced all the injectors in ours for some symptom I no longer remember. However, there was no concrete improvement, so I did not discard the old ones. About a year later, a misfire developed - probably more consistent than yours - and I put one of the old injectors in the problem cylinder. That was the problem. Moral is that the injectors can randomly fail, so unless the PO was trying to fix this same incident you now are dealing with, you had might as well buy a new one - pretty cheap, here - to use as a diagnostic for that problem.

Steve

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'91 MB 190E 2.3
'08 RAV4 Ltd 3.5
'83 Lazy Daze m'home 5.7