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TOPIC: 2009 RAM 5.7L (FUEL TRIM HELP)

2009 RAM 5.7L (FUEL TRIM HELP) 30 Aug 2019 08:52 #1

  • Michael Lee
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I plugged in my obd2 reader (kiwi-3) and took a drive to my son's appointment today watching fuel trims. An hour hwy drive. I noticed something, and want to do something about it!!! All zero's when flooring the accelerator pedal!?!? That's SET fuel delivery trims from the factory right? Even though its GROOVY, prior to my owning the truck, it had ONE owner who always took it to the dealership for everything! I think i need a new computer, what do you guys think?
Usually, the vehicles i groove show an incredible fuel delivery change. From positive numbers (rich) to wayyyy negative! My mileage gains are inconsistent. Sometimes 18 on highway, sometimes 23! I still need to wrap exhaust etc.. But lets get this solved. Im tired of being robbed! What do you guys think?
Michael Lee
Gadgetman Foreston, MN
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2009 RAM 5.7L (FUEL TRIM HELP) 30 Aug 2019 09:25 #2

  • GregK
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what our groove (and other techniques discussed here) SHOULD do is to reduce overall consumption and narrow the range of variation.

fuel trims at zero - all that means is that you (well, the vehicles computers, actually) have successfully re-written the fuel delivery map and the engine/powertrain is optimal.

do you keep track of your mileage/fuel consumption? If not, you should - my instantaneous and average fuel consumption readouts in the car do not match what my fuel tracker app tell me.
consider that the ratio of fuel vapour to air that gets burned changes based on the density of each on any particular day - that means that temperature and pressure have an effect on fuel consumption...MASS air flow sensor, manifold ABSOLUTE pressure sensor, intake air temp sensor...there is no way you'll make a non-stationary engine in an uncontrolled physical environment have rock steady, predictable fuel burn...especially when you add your right foot to the equation.

you don't need to replace your computer; for what it is, the machine is operating as optimally as it can. (Good work!)

EDIT: what does the MAF report in terms of grams/second at idle in closed loop? My understanding is that it should be near the litres of displacement of the engine, in this case 5.7. If it’s above 6, you’ll want to pull that back. MAP modification may be in your future, Michael. Less air = less fuel, remember.
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Last edit: by GregK. Reason: Further thoughts on what should be looked at on the scan tool.

2009 RAM 5.7L (FUEL TRIM HELP) 30 Aug 2019 11:45 #3

  • CLAUDIO CORDOVA
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Hey Michael! I have you tried doing another re-learn and see if those numbers change? I am curious if it does, or if that's your number that its stuck with.

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2009 RAM 5.7L (FUEL TRIM HELP) 30 Aug 2019 15:01 #4

  • GregK
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If he wants to change them from zeros, he’ll have to trick the computer into thinking the engine is running either rich or lean.
Rich is easy: add an EFIE to the upstream o2 sensors. When the voltage offset is correctly applied/adjusted, injector pulse durations will get trimmed back, and you’ll eventually get zeros at the trims again. There’s only so far you can go with it before you get drivability difficulties and/or engine codes.
The computer is working fine, as it should. Unless one can be found that shoots for 20:1 air-fuel ratio, it it doesn’t need replacing.
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