Chevrolet Repair: acceleration problem, 1999 chevy lumina, chevy lumina

Question
Hi I have a 1999 Chevy Lumina sedan. I bought it like 3 months ago and everything seemed to work fine. The 1rst time i took it to the mechanic he said that the transmission wasnt changing gears like its supposed to but he told me the car would be fine. After like 3 weeks the problems started. Everytime i press the gas pedal it runs perfect but if i need to accelerate more than unsual the car starts revin till a point were its like if it was on neutral it only makes sounds and does not accelerate or change gears on its own unless i completely let go of the gas and press it very slowly. whats type of problem could this be? i am thinking either the transmission or something with the fuel injection system because it also wastes gas like a v8. i woulld estimate around 10 miles per gallon... if someone can give me an opinion i would greatly appreciate it!!! thanks!

Answer
Hey,

 You need to have the transmission looked at.  If it isn't upshifting properly because of an electrical problem it might be damaging itself or be too late already.  If a trans doesn't shift when it should late or early it destroys any type of fuel economy or emissions management.

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