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Hello all. I have a 2013 silverado w/5.3l flex vin 7. Basically has rough idle in park and drive. Very poor acceleration. Almost seems to bog down when trying to accelerate. It will occasionally surge and for just a split second I can feel a bit of power.  Also doesn't want to downshift when I lean on the gas pretty heavy. I've got to do near floor it to get it to down ****** and when it does it will drop down 2 gears a lot of the time. No engine light and it won't set any codes. Showed 0 misfires on all cylinders. Long Fuel trims usually in single digits negs. Fuel pressure 43-46psi at idle and highway. I've replaced throttle position sensor, Accelerator pedal position sensor, manifold pressure sensor, mass air sensor, plugs, coolant temp sensor, oxygen sensors. Fuel pump, intake manifold gaskets twice (now with "updated" steel gaskets), throttle body gasket/seal, injector o-rings (upper and lower). Tested all coils for strong spark. Smoke tested for vac leaks along with propane. It has never failed to start or even had a long start and has never died/stalled. I'm just kinda at a loss at this point. Any help will be appreciated and possibly considered. Thanks

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Supposedly my fuel pressure is normal with the flex fuel. The ECM regulates the fuel pressure depending on the alcohol content percentage. Enclosed loop it has almost 70 PSI and drops down to about 45 in closed loop. And there's no exhaust restriction. it has no cats. The downstream O2 sensor readings mirror the upstream

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Fuel sys 1 CLOSED LOOP

Fuel sys 2 CLOSED LOOP

Calc load 16.3 (%)

ECT 196 (°F)

STFT B1 -2.3 (%)

LTFT B1 4.7 (%)

STFT B2 0.0 (%)

LTFT B2 -2.3 (%)


MAP 9 (inHg) / (kPa)

Eng RPM 602


SPART ADV. 18 (°)

IAT 84 (°F)

MAF 0.69 (lb/min) / (g/s)

Abs TPS 15.3 (%)

O2 B1 S1 0.748 (v)

STFT B1 S1 2.3 (%)

O2 B1 S2 0.659 (v)

O2 B2 S1 0.820 (v)

STFT B2 S1 0.0 (%)

O2 B2 S2 0.255 (v)

Command EVAP 20.4 (%)

Fuel level 87.7 (%)

EVAP VP -0.2 (InH20)

BARO 30 (inHg)

CAT TEMP B1 943 (°F)

CAT TEMP B2 943 (°F)

ECU volts 14.3 (v)

EQ Ratio 0.999 (%)

Relative TPS 1.6 (%)

Ambient 66 (°F)

TPS B 14.9 (%)

ACC Pedal D 21.2 (%)

ACC Pedal E 11.0 (%)

Command TAC 2.4 (%)


ALCH PCT 3.8 (%)



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It does seem to run a little better before going into closed loop. 


Also, I feel like it goes into OL-Drive "open loop drive"/fuel enrichment prematurely. I'm not certain when it's supposed to kick in but it will sometimes with less than half throttle. The engine load increases very quickly with light throttle. Esp in those times where it just kinda lugs or bogs instead of downshifting and taking off when I'm trying to accelerate at a higher speed. 


Another odd thing about a month ago was that my calculated alcohol content percentage gradually increased every time I got fuel until it got to 78%. and it leveled off and stayed until I reset it a few weeks ago. But during that time, it ran a lot better when it was running so rich and fuel trims were maxed out in the negs. Had much more power then but millage was terrible. 

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open loop normally comes on after a few minutes of drive time or some certain conditions are not being met. 


Have you pressure tested your injectors with the scan tool? 

I still feel like the fuel pressure is low. Have you checked vacuum hoses?

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