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Q: 99 GMC SUBURBAN running lean and starving for fuel when stompped on.

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Issue...5.7 vortex factory rebuild installed 5 years ago 30,000 on it, starving for fuel when stomped on. Truck idles and runs well except when you try to accelerate. it responds and revs up to4000 rpm but will not shift and battery light comes on until you back off accelerator ??????? Has been doin this for a while.......6 months or so... been to a few repair shops lots of money but nobody can figure it out. Things done to it , starting with most recent....Took to tuner shop had adjustments to ecm done for larger tires thought shift points were off , didnt work, guy said the motor is calling for 30% more fuel ? SAYS NEEDS TO PUT ON DYNO AND ADJUST FUEL TRIMS....THIS IS A STOCK MOTOR. COULD THE FUEL PUMP possibly be the issue ? in the past few months replaced.. spider, fuel filter, tps,idle control valve, cleaned throttle body, new catalytic converters. Fuel pressure at the motor 59psi. took to 2 different trans shops and they say it aint trans . Any input before taking to dealer

My car has 30000 miles.
My car has an automatic transmission.

Hi there. Is there a check engine light on? If so, what are the codes, freeze frame data? Stored codes and data will aid in diagnosing what is occurring. What does the data look like from the O2 sensors? Which fuel trim is at 30%, short or long? Hopefully this is a short term fuel trim reading. Has a compression test or cylinder leak down test been performed? What were the readings? What is the data from the air flow meter and map sensor? If one or both of these are providing the ECM with false data then this could be the diagnostic path to take. Has the battery and alternator had a proper test performed? A failing battery, especially if it has a bad cell, will cause a multitude of problems. I suggest having a qualified technician perform an inspection. Your Mechanic has several available technicians that can assist you with a car hesitates inspection.

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