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9.8 mile a gallon in 2007 gt 3.5

961 Views 4 Replies 2 Participants Last post by  BrettsG6GtConv
I know im becoming a problem child but i do own 2 of these lo. In all seriousness I do love these cars but at same time 9.8 mile a gallon is is worse than my old 84 z28 Camaro with 5.0. I have no lights on dash, no stored codes, just changed, oil, plugs, wires, air filter and that stupid ground wire. Question is what else could this be. I had a qtr tank of gas yesterday and drove roughly 18 miles and was on empty if that helps.
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If you have access to a scan tool you should be to see your short and long term fuel trims. This is an indication of how much fuel the PCM is trying to add or remove in order to maintain an appropriate air fuel ratio. I guess the main inputs would be the MAF which is on the tube just after the air box. This can be cleaned with the appropriate cleaner. The other side is the first bank of O2 sensors. Poorly flowing injectors can restrict flow and cause the PCM to compensate. Closer to zero on the long term fuel trims would indicate the PCM is not having to compensate from the original factory settings.

If it were mine, I would check the fuel trims, clean the MAF, add a couple of bottles of gumout cleaner (or whatever brand you prefer) in the tank to clean the injectors and see if it improves once you have finished the tank of fuel. Those are the simple things I would try before I dug deeper. Hope it helps and you can get it fixed
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Just to update and close this post, both downstream oxygen sensors where bad. Replaced and even the city driving which basically all i do is at 17 mpg avg. up from 9. Assuming all is fixed. Thanks for your help it is always appreciated.
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