Enzo250

My dad has a 94 GXE and has been having a problem. The check engine light has been coming on for a while now and when it would come on the engine would idle rough and misfire. But after a minute the light would turn off and the car would run fine again.. SO I told him dont worry about it to much it goes away.. But now the light is on all the time and the car misfires badly. SO i checked the code and it's coming back as code 51. Which is "injector circuit". SO I immediately figured i had a bad injector. SO one by one i removed the connector for each injector(expect one of them) while the engine was running to see if it would make a difference. Every one seemed to be working. NOw the problem is there's one injector thats under the intake manifold. Why is it that it's always the one that you can't get to. SO now im stuck. I've tired listening to every injector and they all seem to be ticking fine. Where's the problem? i want to go get a new injector and replace that one but what if thats not the problem? Has anyone had the same problem? Thanks...