Not sure that PROM Flash was a good idea!!!

Discussion in 'Performance & Fuel' started by Quincy, Aug 13, 2010.

  1. Quincy

    Quincy New Member

    Shortly after getting my new [to me] "06 5.3 Silverado I discovered that the dealer owed me a PROM Flash. I went to the local Chevy dealer and asked if they thought it was a good idea and of course they thought it was just great.

    My MPG seemed to be running about 16 at the time so I thought it would probably make a difference so I decided to go ahead with the flash. What do you know, I was right. My MPG changed all right, it went to 14.6.

    Now i am wondering if I can have him put it back.

    Does any one have any input for me here. I am hoping to use this truck for towing our camping trailer and would like some insight as to what I can do to correct this.

    I also have some follow up questions but cant work them out until I get some idea from you guys what might be happening here.

    I have not towed after the Dealer "fixed me up" here but before the experts got to it I was getting almost 13 pulling that heavy trailer about 7000lb.

    I am thinking I should have left it alone but if that were the case then why would they make it so we can get under the hood?

    My only mod was a CAI.

    Hopefully somebody out there can get me on the right track.


    Last edited: Aug 13, 2010
  2. silveradotrailblazer

    silveradotrailblazer Epic Member 5+ Years ROTM Winner 5000 Posts

    How many tankfuls did you run before and after the flash?
  3. Quincy

    Quincy New Member

    Thanks for the response SilveradoTB

    Before the flash I ran the truck for about four months. I put the CAI on and after what seemed like 100 miles or so the ECM woke up and the mpg moved up to just under 17mpg. I then put the stock air cleaner back on and tried an Edge Programmer and the mileage returned to about 15 mpg in the economy mode a little better in stock mode. As I am sure you know they do not like running anything but stock parts with their programmer. I checked and the air cleaner from Chevy is supposed to be the high flow model {one wonders why they even have a low flow air cleaner} After no success with the programmer I put the ECM back to stock and went to my local Chevy Dealer to get my Prom Flash. After the flash I ran about four tankfulls through it and it settled at 14.5 Now I have put the CAI back on and after two or three tanks with no increase in mpg [thats right after the flash I did not get the increase in mpg with the CAI installed]have just set the programmer to economy about forty or so miles ago so I can not judge if this will make a difference. I can tell you it is up to 14.7 right now.

    Any input you can offer will be welcome.

    Again, thanks.

  4. silveradotrailblazer

    silveradotrailblazer Epic Member 5+ Years ROTM Winner 5000 Posts

    Does you truck have the DIC gauges and if so are you gong by this number or are you figuring your mileage by hand.
  5. Quincy

    Quincy New Member

    DIC... but I do not expect this to be accurate mpg, however if I go from stock to economy with the programmer I would hope the mpg would go up at least a little. Same as when I put the CAI on before the final PROM flash. I saw an increase in mpg but after the flash, when I put the CAI on, it pretty much stayed the same.

  6. silveradotrailblazer

    silveradotrailblazer Epic Member 5+ Years ROTM Winner 5000 Posts

    I've found that what the DIC says and by hand are ALWAYS different.
  7. Sam_A

    Sam_A Rockstar 100 Posts

    I use the "GasCubby" app for the iPhone to keep track of all of my vehicle maintenance and mpgs. The DIC on my 03 2500 6.6L is giving me an average of 19.9mpg on my recent trip to NC (total of 2,200 miles, mostly hwy). The iPhone app was giving me an average mpg of only 15.9! Not sure how the DIC makes it's calculations, but it's a big difference from the app calculations (Miles Driven / Gallons filled).

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