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Vehicle came from another shop, has new distributor, AC delco plugs and wires, New spider injection, Bank 2 Sensor 1 oxygen sensor is New. The truck develops a slight, random miss at idle, can hardly feel it, when looking at misfire data, it has misfires on cyclinders 1-4, and ive never seen or 5 or 6 misfire, MAF at idle reads about : 4.7. Map Sensor Reads 10 to 11 at an idle. 02 sensors seem to be switching well, however when looking at fuel trim, after idling for periods of time short term fuel trim will be -7 and continiously take fuel away. I can add propane and misfires completely go away, Im stumped why it would constantly be taking fuel away, when fuel is added it runs correctly.
Was the pressure regulator in the intake manifold checked to see if it is leaking? If its not leaking i would be leaning towards the 02 or a bad new injector.
