We replace many connector pigtails to EFI fuel injectors; check that the connector is tight and the spring lock is still there and engaging with a "click.” That type of problem could be intermittent. To check the injector itself requires an ohm meter to take a measurement between the two terminals. Resistance should be between 10 and 14 ohms. If it is outside that range, it's probably failing, could work intermittently and will soon stop working. Replace it.
Chino Autotech Inc.
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