2004 Silverado Horrible Mpg + P0449 Cel

[dminor09]

Ok, Here's the deal. I just purchased my first Truck. Got a 2004 Chevy Silverado 2wd 5.3 V8. I have a K&N air filter, duel flowmaster exhaust. The truck has 145,000 miles on it but runs wonderfully. I did put 265/75/16 BFG A/T tires on it which are slightly oversize from stock. I am getting consistantly 12-13 MPG I don't understand what the problem is. I drive it very tenderly and most of my driving is HWY mileage. I pass all emissions test for the city i live in. The only thing that seems to be possible responsible is the p0449 CEL. I have read losts of info about this problem and none of them has expressed a bad loss of MPG b/c of this. I'm completely lost on this one. Does ayone have any suggestions on how to boost MPG other then Cold air intake....programer...ect..I'm really interested in fixing the problem. Does anyone know if this p0449 CEL could be my problem...which case i would replace the EVAP cannaster, or EVAP vent valve. I appreciate any suggestions.

[99silveradoz71]

Welcome aboard

[SeirraRR]

Welcome to the site

[OldCrLvr]

Welcome Aboard, I have no insight for you but I can tell you my 00 5.3 4x4 gets 14-16 depending on how I drive it.

[txab]

Welcome.

 

What was your original tire size?

[Nytemare]

P0449 Evaporative Emission Control System Vent Valve/Solenoid Circuit

 

Sounds like its the Solenoid that's failing. wont affect your fuel economy much though.

 

12-13MPG is about average for your truck man.

 

I get 14.33MPG in my truck...I have a tune and I run a K&N filter and full synthetic oil in my drivetrain. I also have a dual exhaust and highway thread tires.

Stock it got 10.75MPG...or as high as 11.2MPG

I do mostly highway driving also and I burn 94 octane...its over 5 bucks a gallon

 

I would say you are doing good.

 

For further explanation about your fuel economy see the quote in my sig.

[redvett]

If you didnt have the speedo calibrations changed from the 245's fix that first. When was it or has it ever been tuned up? Also fix the P0449.

[grayghost7]

Is yours a reg cab or extended?

[dminor09]

it's a extended cab, i'm working on the P0449 fix....wow i thought that i would be able to get about 16 mpg. I have a buddy with the a 2003 Z71 5.3l same exact truck except mine is 2wd..and i have k&n...he get's 16-17 consistantly.....so i just assumed that my newer truck would be able to match that. oh and did i mention he is running 285/75/16 MT tires....maybe i'm asking too much..I just want to get the best out of my truck..i'll post some pic's soon...thanks for the reply's...Where can I get the speed calibrations done at?

Daniel

[redvett]

My 04 averages 17 mix city/hwy and my 03 does the same. Non OEM heaver tires will hurt fuel economy.

[txab]

If you didnt have the speedo calibrations changed from the 245's fix that first. When was it or has it ever been tuned up? Also fix the P0449.

 

Depending on your OEM stire size you can have a 5-7% difference in odo/speedo readings

[grayghost7]

Mine gets 17.5 [rcsb 4x4] average and most I've talked to are getting 14-16 average in their extended cabs.

[zedbear]

Mine seems to be getting around 14-15 around town. Haven't taken it on an all highway trip yet.

[Nytemare]

it's a extended cab, i'm working on the P0449 fix....wow i thought that i would be able to get about 16 mpg. I have a buddy with the a 2003 Z71 5.3l same exact truck except mine is 2wd..and i have k&n...he get's 16-17 consistantly.....so i just assumed that my newer truck would be able to match that. oh and did i mention he is running 285/75/16 MT tires....maybe i'm asking too much..I just want to get the best out of my truck..i'll post some pic's soon...thanks for the reply's...Where can I get the speed calibrations done at?

Daniel

I have no idea man....your 2wd should get better economy than his 4x4.

But like I said....I think your doing good getting 13MPG without a tune...I only got 10-11 with my truck.

 

Get it recalibrated at the dealership and get back to us.

[txab]

Also, what's the rear ratio on your truck?