1,000 miles later the gas mileage is slowing going up, the performance seems to be come and go but now I got an CEL for P0172 and at the same time started shifting rough, but smoothing out after a little bit. After the hard shift I thought for sure the CEL was going to point to the solenoid on the valve cover but it's a rich condition.. anyway here is some freeze frame data for the code:

Vehicle VIN: 3GNDA23P56S515233
Vehicle Manufacturer: Chevrolet
Vehicle Calibration ID: 126

Freeze frame information:
------------------
Fuel Status = 0 byte
Engine Load = 25.882 %
Engine Coolant Temperature = 199.4 °F
Fuel Trim Bank 1 Short Term = -5.469 %
Fuel Trim Bank 1 Long Term = -20.312 %
Intake Manifold Pressure = 4.496 psi
Engine RPM = 688.5 rpm
Speed (OBD) = 0 mph
Timing Advance = 2.5 °
Intake Air Temperature = 86 °F
Mass Air Flow Rate = 2.68 g/s
Throttle Position(Manifold) = 14.118 %
Run time since engine start = 345 s
Fuel Level (From Engine ECU) = 58.431 %
Evap System Vapour Pressure = -4,113.75 Pa
Barometric pressure (from vehicle) = 14.214 psi
Catalyst Temperature (Bank 1,Sensor 1) = 1,236.2 °F
Voltage (Control Module) = 12.774 V
Engine Load(Absolute) = 16.471 %
Commanded Equivalence Ratio(lambda) = 1
Relative Throttle Position = 3.137 %
Ambient air temp = 75.2 °F
Absolute Throttle Position B = 14.118 %
Accelerator PedalPosition D = 19.216 %
Accelerator PedalPosition E = 9.412 %


End of report.

 

it is running awful hot.
P0172 does not mean running rich. It means that the fuel trim is rich as the computer can make it. Because there is too much air in the A/F mixture.

The short term should be between +10 and -10 near 0 optimum
the long term should be the same.

 

Yeah I was reading around this forum and saw that was mentioned a lot. I thought it was odd that it could be caused by an air leak and I just fixed a big leak that never threw a code at all... I have all new injectors from fixing a misfire.. cleaned the TB.. fuel pressure is within specs, including the leakdown test (I double tested this because my performance feels/acts like a clogged fuel filter but I know there is no inline filter to service).. cleaned the air flow sensor with the proper cleaner.. all this done about 1,000 miles ago. Air filter is still somewhat clean.. it's definitely been dirtier.

 

Also just to note it does have the ac Delco thermostat that has been mentioned in this forum and I do a lot of stop and go driving.

 

have you checked the flex pipe? the EVAP purge valve (normally closed)? the vapor line? Do you have an after market air filter or exhaust system?

t-stat does not make for over heating; it's job is to keep the temp above 180F. The radiator/fan keeps it down.

 

fan kicks on, not sure at what temp tho but I do hear it run and it's on when the ac is on for sure.

I've had a p0446 code for years now, I tried replacing the purge valve under the hood, the vent canister in the back, and the gas cap. none of those worked but because we don't have emissions testing in my state i haven't worried about it. However I did have trouble at the pump filling up for the first time and it lasted about a week but that has gone away.. I will replace the vent.. I will go check the purge valve under the hood now and see if i can find the flex pipe.

I do not have an after market air filter or exhaust. all repairs and part numbers have come from using this forum.

 

A friend ha a persistent P0172 that went away after he got a new fuel pump.
P0446 means the EVAP vent is NOT venting. Nothing to do with gas cap etc It would be the vent valve stuck closed/obstructed or the charcoal canister clogged.

 

The Purge valve is closed. The flex pipe looks fine, no signs of any soot. Same for the gas lines around the back driverside tire. No rust nothing looks wet nothing smells

 

Is it possible that it's been running with the leak so long that now it's fixed the computer is having a hard time with the data? I read in another thread that resetting the fuel trim fix his problem, although mine starts just fine unlike his

 

Have you tried a full 30 minute battery lobotomy.