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Thread: 2008 Pontiac G8 tune issues.

  1. #1
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    2008 Pontiac G8 tune issues.

    Hello all. I had my car tuned (2008 Pontiac G8 GT. Rotofab intake. 145,000 miles) by a "professional" that came highly recommended. Was initially happy with the tune and the performance of the engine and transmission. I called and asked him to make a few tweaks to the transmission tune and things got hairy from there. He shortened the shift time (not a technical term. I mean he made it shift faster) in the TUTD mode and I was very pleased with the results. After a few months of driving I started to get some flaring in my shifts and some slow lazy shifts. I also tried racing a few times and now my car will not break 139 mph. I am now back to my "stock" tune and needing help. Tunes attached for your viewing pleasure. Any help will be greatly appreciated!
    Attached Files Attached Files

  2. #2
    How is it shifting with stock tune?. sounds like it still has problems with stock tune.
    i'm not a tuner- a dealer tech- . since it was good for a couple months and now very bad even with stock tune = sounds like you burnt up your transmission. These transmissions can not handle too much fast shift abuse.Especially at higher mileages. Can you pull a sample of fluid? (under car- grab a small cup/glass and with engine off (and cold so you dont burn yourself when re installing plug) unscrew the level plug on the trans pan- pull not more than a couple of ounces to check (or you'll be needing to add after and that's harder).
    if its dark-black and has a god awfull smell- chances are you burnt up some clutches or damaged the torque. A tune can not repair mechanical failure.

  3. #3
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    I live in the sticks and haven?t built my shop yet. I tried to get it up high enough to get under it to check. That didn?t turn out well. All I have to work off of is sandy dirt. The jack stands sunk and the car fell and it took me for ever to get them out. As for the shifting it shifts very well under full power with both tunes. But it flares crazy bad with custom tune under normal driving conditions. Does that help? That is why I feel it is in the tune.

  4. #4
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    G8 owner here. Post tune and log files, please?
    Daily Driver= 2003 BMW 330xi
    Weekend Cruiser= 2009 Pontiac G8 GT (Vararam, TSP LS3 N/A Stage 1, OBX, CTS-V converter, MagnaFlows w/ J-Pipes, 160 t-stat)
    Project Car= 1991 Chevrolet Camaro RS (LQ4 w/ Gen 4 Rods, LS3 heads, turbo...)
    Truck= 2007 Chevy Silverado 1500 LT LY5 4x4

  5. #5
    just a few things. Your MAF curve sucks, Your PE table sucks, Your timing table kind of sucks, your final minimum spark sucks, your shift timing is way too fast, Your max line is too high, your on coming presets are stock. Did you pay someone to do this??? Do you have a wideband?? I need to help a fellow G8 owner.

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    I will take a look at the files later...

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    I apologize I have not responded to any of your responses. I am a fireman and deputy sheriff and this coronavirus stuff has been Unlike anything I?ve seen in my almost 24 years of service. I have to get my laptop set up to repost the tune file and log files. For some reason it will not let me get to the ones I posted already. Again thank you for the responses.
    Last edited by gibbsracin; 05-14-2020 at 10:00 AM. Reason: Misspelling

  8. #8
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    Sounds like a Pat G tune or some other mail order type tune. I had similar issues with mail order tunes in the past. They tell you a wideband is not needed to tune your car. Well, obviously that's not true. I did the mail order tune before, too much is left on the table for what your paying for. Would never do it again IMO. I suspect they are only using fuel trims to dial in your fueling and adjusting your timing based on knock. I dont see how its possible to get the tune even close using those methods.

  9. #9
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    Quote Originally Posted by jaydubb71 View Post
    I will take a look at the files later...

    Jaydubb I am finally able to sit down with a good connection and my laptop. Do you have any recomendations?

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    Any help would be greatly appreciated! I know I am very slow to reply but as I stated I stay crazy busy!

  11. #11
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    Quote Originally Posted by gibbsracin View Post
    Hello all. I had my car tuned (2008 Pontiac G8 GT. Rotofab intake. 145,000 miles) by a "professional" that came highly recommended. Was initially happy with the tune and the performance of the engine and transmission. I called and asked him to make a few tweaks to the transmission tune and things got hairy from there. He shortened the shift time (not a technical term. I mean he made it shift faster) in the TUTD mode and I was very pleased with the results. After a few months of driving I started to get some flaring in my shifts and some slow lazy shifts. I also tried racing a few times and now my car will not break 139 mph. I am now back to my "stock" tune and needing help. Tunes attached for your viewing pleasure. Any help will be greatly appreciated!
    Do you have logs of the issues? If so post them.
    If you have a complete list of modifications please post that.

    Something to think about. It has run fine for months what changed??? Make sure there is not a mechanical issue. Glad to help.
    Last edited by jsllc; 07-15-2020 at 01:54 PM.
    2012 ZL1 - Maggie Heartbeat, Port & Polish Heads, Custom Cam, Custom rotating assembly, steel sleeved LS9, No NOS and No water meth. 16psi
    810rwhp and 820rwtq 91 Octane 6400 rpm
    948rwhp and 951rwtq 105 Octane 6400 rpm
    999rwhp and 997rwtq on 60% Ethanol 6400 rpm

  12. #12
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    Check your trans fluid as well.
    2009.5 PBM G8 GXP M6 W/Roof-Self tune, OBX LTs, Kooks axleback, LSA blower, cam,
    Monster LT1-SC clutch, flex fuel, 12 psi [email protected] 1,800 D.A
    2007 TBSS-Self tune, bolt ons [email protected], 1,900 D.A
    1991 GMC Syclone- Self tune/catback 12.8@104, 4,200ft D.A

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    Quote Originally Posted by gibbsracin View Post
    Any help would be greatly appreciated! I know I am very slow to reply but as I stated I stay crazy busy!
    I'm just a rookie tuner, but in reading all the comments, especially the one saying many of the calibration changes made sucked, I think one possibility I'd consider is that the tuner you had working on the car, may have f**ked-up the trans cal such that your high mileage trans was damaged. I think I'd sample the ATF and drop the trans pan and see how much clutch residue and/or metallic powder is in the bottom of it.

    Also, as your a deputy and a firefighter....thank you for your service.
    Hib Halverson
    Just Another Tuner in Training.

  14. #14
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    change transmission oil and the filter see if there is any changes.
    Abdulaziz T Hadi - E-mail: [email protected]

  15. #15
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    I'm assuming that this is a 6l80/90 trans..... When you did your changes did you do a reset / preset. read this thread https://forum.hptuners.com/showthrea...highlight=6L80.
    There are other threads about shifting issues with a 6L80 in the transmission section. I had issues with my STS V 6L80, mine was the TCM. Got a Dorman rebuilt TCM swapped them all was good.

  16. #16
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    fellow G8 owner here