Page 1 of 5 12345 LastLast
Results 1 to 20 of 81
Like Tree3Likes

TERRIBLE GAS MILEAGE!! Really upset..

This is a discussion on TERRIBLE GAS MILEAGE!! Really upset.. within the Firebird / WS6 forums, part of the Vehicle Specific category; okay here it is.. I have a 99 3.8 Firebird. I AM GETTING 13MPG Houston TX City.. The engine is ...

  1. #1
    Member flybird's Avatar
    Join Date
    Jun 2010
    Location
    Houston
    Posts
    408

    Mid Night Blue
    1999 Firebird 3.8 series

    TERRIBLE GAS MILEAGE!! Really upset..

    okay here it is.. I have a 99 3.8 Firebird. I AM GETTING 13MPG Houston TX City..

    The engine is brand new, not just rebuilt with old parts. Im talking about from bottom to top everything is GM new including long block. Engine is bored over .30 and heads are shaved.

    Everything I have replaced bc of this bad MPG problem are Fuel Filter, Fuel Regulator, Spark Plugs, O2 Sensors, Knock Sensor, Knock Sensor Wiring. I had several codes and when i replaced all of these items, they are gone now. I repeat I have NO CODES. I am very aggrivated bc this is not making any sense to me. I drive to school and work and to home. I range 2000 rpms and 2500 rpms so i can improve on my MPG.

    MODS: just a K&N Cold Air Intake and Performance chip.

    I am very lost... I have no idea what to do. The reason I have a v6 is to save money for school.. This is really annoying and making me want to get rid of this...

    Any help??

  2. #2
    Super Moderator
    pajeff02's Avatar
    Join Date
    Feb 2009
    Location
    Mansfield, PA
    Posts
    21,576

    Black & Blue
    '02 WS.6 / '07 Suburban

    What sort of mileage are you expecting? Auto or stick?

  3. #3
    Spaz is My Mentor SMWS6TA's Avatar
    Join Date
    Feb 2009
    Location
    Ugy Lower Corner of AL
    Posts
    10,511

    Navy Blue Metallic
    98 T/A w/a little mods...

    First clean the MAF. K&N filters no matter how good you let them dry have oil in them and as the air passes through the filter it picks up oil with then attaches to the MAF sensor. Use some MAF cleaner, you can pick it up from any parts store. Spray and let dry do not use a towel.

    Either ditch the K&N and use a paper filter or get use to cleaning the MAF every few weeks


    2nd - performance chip - this could be the main problem. They do go bad, are you able to disconnect and run with stock tune?



    Contact this member - Smittro


    he is our resident V6 guy.

  4. #4
    Senior Member Too Fast's Avatar
    Join Date
    Nov 2006
    Location
    Indianapolis
    Age
    54
    Posts
    5,170

    Black
    2000 WS6 6spd Hooker LT

    +1 on the MAF being contaminated.

  5. #5
    Member chris1974's Avatar
    Join Date
    Jan 2012
    Location
    Houston
    Posts
    225

    Bright Red
    1998 Firebird Formula LS1

    +1 on the chip. The whole motor is new and running on the old tune?

  6. #6
    Member flybird's Avatar
    Join Date
    Jun 2010
    Location
    Houston
    Posts
    408

    Mid Night Blue
    1999 Firebird 3.8 series

    its an auto

    I cleaned the MAF sensor roughly 2 weeks ago. But i do hear what your saying. Clean it every so often makes sense. I can disable chip now. I had no idea that they can go bad??? I bought a expensive one too.. Not one of those cheap ass $40 ones. But yeah i will pull it off.

    I was starting to think that i had a fuel leak(checked did not find one) or some1 around this area were siphering gas. (Im sure i spelled siphering wrong) lol

  7. #7
    Moderator 35th-ANV-SS's Avatar
    Join Date
    Oct 2008
    Location
    Wherever life takes me
    Posts
    12,465

    Red
    02 35th LE Camaro SS

    Other than terrible gas mileage, how is the car running overall?

  8. #8
    Member flybird's Avatar
    Join Date
    Jun 2010
    Location
    Houston
    Posts
    408

    Mid Night Blue
    1999 Firebird 3.8 series

    Good! No problems, no missfiring, sometimes after a warm start it has abit of a stumble on start like it hasnt got fuel to start but nothing major.

  9. #9
    024mula 024mula's Avatar
    Join Date
    Dec 2010
    Location
    Ohio
    Age
    57
    Posts
    680

    silver
    '02 Firebird Formula

    Back to the Basic...........Is the emergency brake cable stuck?

    Or check the fuel line after the fuel pump by running the car and about 1500 RPM for about 15 mins and check if there is fuel under the car.

  10. #10
    Moderator 35th-ANV-SS's Avatar
    Join Date
    Oct 2008
    Location
    Wherever life takes me
    Posts
    12,465

    Red
    02 35th LE Camaro SS

    My next question was do you smell fuel at all.

  11. #11
    Member flybird's Avatar
    Join Date
    Jun 2010
    Location
    Houston
    Posts
    408

    Mid Night Blue
    1999 Firebird 3.8 series

    Checked for leaks none. Ill do what you said run it 1500 rpms. And no brake is not stuck.

  12. #12
    Member flybird's Avatar
    Join Date
    Jun 2010
    Location
    Houston
    Posts
    408

    Mid Night Blue
    1999 Firebird 3.8 series

    No none at all. Checked for smells often. Nvr.

  13. #13
    Super Moderator
    pajeff02's Avatar
    Join Date
    Feb 2009
    Location
    Mansfield, PA
    Posts
    21,576

    Black & Blue
    '02 WS.6 / '07 Suburban

    Other things to check that make a difference -- correct tire pressure, wheel alignment in spec, any brakes dragging (in addition to the parking brake), plugs and wires in good shape, etc. What is your rear gear ratio?

  14. #14
    Member flybird's Avatar
    Join Date
    Jun 2010
    Location
    Houston
    Posts
    408

    Mid Night Blue
    1999 Firebird 3.8 series

    Tires are brand new, 600miles z rated. Pressure, balance, alignment is all correct. Calipers stick just a tad but not much to make a difference. Rear end is stock. Limited slip 3.23.. Plugs are new and wiring, 300miles.

  15. #15
    Senior Member Too Fast's Avatar
    Join Date
    Nov 2006
    Location
    Indianapolis
    Age
    54
    Posts
    5,170

    Black
    2000 WS6 6spd Hooker LT

    What about the engine temp. If your thermostat is not there, or is opening way too soon, then it will usually throw a code, but not right away. If it is always running below ~165, then the pcm has the car running way rich. I've seen this happen before....check engine temp with a scan tool preferably, for more accurate readings.

  16. #16
    Next... MrKid's Avatar
    Join Date
    Sep 2009
    Location
    Milford, CT
    Posts
    626

    Red
    '68 Camaro RS, '11 Camaro

    How many miles on the rebuild? Gas milage improves after break in.
    Are you running cats? Are they original? They can clog a bit without throwing a light.

  17. #17
    Veteran 0rion's Avatar
    Join Date
    Aug 2005
    Location
    ohio
    Posts
    22,520

    98 Formula
    06 duramax

    any exhaust leaks pre O2's? Is there an excessive amount of soot inside the exhaust tips? What "chip" do you have? Is it an iat tricker or does it flash the pcm?

  18. #18
    ʢ ൧ ൨ ൩ ൪ ൫ ൬ ൭ ൮Ր Ց Ւ Փ Smittro's Avatar
    Join Date
    Feb 2009
    Location
    Pittsburgh
    Posts
    9,965

    White
    2008 Hummer H3

    Quote Originally Posted by flybird View Post
    Good! No problems, no missfiring, sometimes after a warm start it has abit of a stumble on start like it hasnt got fuel to start but nothing major.
    Quote Originally Posted by flybird View Post
    okay here it is.. I have a 99 3.8 Firebird. I AM GETTING 13MPG Houston TX City..

    The engine is brand new, not just rebuilt with old parts. Im talking about from bottom to top everything is GM new including long block. Engine is bored over .30 and heads are shaved.
    Everything I have replaced bc of this bad MPG problem are Fuel Filter, Fuel Regulator, Spark Plugs, O2 Sensors, Knock Sensor, Knock Sensor Wiring. I had several codes and when i replaced all of these items, they are gone now. I repeat I have NO CODES. I am very aggrivated bc this is not making any sense to me. I drive to school and work and to home. I range 2000 rpms and 2500 rpms so i can improve on my MPG.

    MODS: just a K&N Cold Air Intake and Performance chip.

    I am very lost... I have no idea what to do. The reason I have a v6 is to save money for school.. This is really annoying and making me want to get rid of this...

    Any help??
    Quote Originally Posted by flybird View Post
    Tires are brand new, 600miles z rated. Pressure, balance, alignment is all correct. Calipers stick just a tad but not much to make a difference. Rear end is stock. Limited slip 3.23.. Plugs are new and wiring, 300miles.

    1) .30 over and shaved heads but no tune,

    2) performance chip for a non modified 3800,

    3)hung calipar,

    4) K&N junk filter system..

    All can contribute to poor MPG's..

    13-14mpg city is about right for these considering they only get ~26 mpg's highway but no tune after internal mods is likely going to be your issue here..
    :\Users\Steven\Pictures\d6ftg5nh.gif


    Suggestion: If you are particularly irritated by another member's posting habits and are constantly fighting the urge to flame them, you can click on that person's profile, and select "Add to ignore list." This will make that person's posts invisible to you.

  19. #19
    Former Mopar Man 2002ssslp's Avatar
    Join Date
    Jun 2011
    Location
    Branchville, NJ
    Posts
    3,111

    Silver & Blue
    02 Camaro SS, 04 GTO

    Quote Originally Posted by flybird View Post
    okay here it is.. I have a 99 3.8 Firebird. I AM GETTING 13MPG Houston TX City..

    The engine is brand new, not just rebuilt with old parts. Im talking about from bottom to top everything is GM new including long block. Engine is bored over .30 and heads are shaved.

    Everything I have replaced bc of this bad MPG problem are Fuel Filter, Fuel Regulator, Spark Plugs, O2 Sensors, Knock Sensor, Knock Sensor Wiring. I had several codes and when i replaced all of these items, they are gone now. I repeat I have NO CODES. I am very aggrivated bc this is not making any sense to me. I drive to school and work and to home. I range 2000 rpms and 2500 rpms so i can improve on my MPG.

    MODS: just a K&N Cold Air Intake and Performance chip.

    I am very lost... I have no idea what to do. The reason I have a v6 is to save money for school.. This is really annoying and making me want to get rid of this...

    Any help??
    You have some issues here. Take it to a good Dyno shop and have everything tested. My 02 SS with 350rwhp gets 17 city and 27 hwy. I think it may be your computer.

  20. #20
    ʢ ൧ ൨ ൩ ൪ ൫ ൬ ൭ ൮Ր Ց Ւ Փ Smittro's Avatar
    Join Date
    Feb 2009
    Location
    Pittsburgh
    Posts
    9,965

    White
    2008 Hummer H3

    Anytime you change displacement and mill heads you're going to need a REAL tune..

    ESPECIALLY, with a drive by wire TB.

    A "performance chip" which is'nt really too usefull on OBD2 cars anyways is NOT, or even near to, a real tune..
    Last edited by Smittro; 02-14-2012 at 06:29 AM.

Page 1 of 5 12345 LastLast

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. Help: Terrible gas mileage!!
    By flybird in forum V6
    Replies: 59
    Last Post: 08-04-2013, 08:41 PM
  2. I think Tony got a little upset...
    By SMWS6TA in forum Almost Anything Goes
    Replies: 3
    Last Post: 08-27-2012, 09:55 AM
  3. alittle upset
    By jaslivers in forum Request and Feedback
    Replies: 11
    Last Post: 12-28-2009, 09:01 PM
  4. Very upset over my new ftp clear lid
    By brian r in forum General Help
    Replies: 3
    Last Post: 09-19-2009, 01:27 PM
  5. terrible fuel mileage
    By Dennis McInroy in forum General Help
    Replies: 5
    Last Post: 07-02-2007, 09:26 PM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •