Q: 1st Injector Firing Improperly on 1994 Jeep Grand Cherokee

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Jeep runs fine for abt 10 minutes then kinda sputters, but doesn't loose power. Had diagnotic done and it said 1st injector firing improperly. Mechanic said this is not a typical problem on jeep, and would need time to properly diagnose. Suspects it is the computer, but says this is not a common problem on jeeps.
Have has stalling issues in the past, replaced: throttle position sensor, coil, crank shaft sensor.
Any ideas or advice? I'm a girl and need some advice, thanks!
(1) Answer
How are the other injectors firing? Did your mechanic try a know good injector ( from another cylinder ) to see if it is a driver problem or an injector problem? I have seen a lot of issues with the harness on the 6 cyl Jeeps. It could be a frayed harness, from oil leaking on it. Good Luck!