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  1. #1
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    Default Diagnostic help. Pcm issue? Other problem?. 07 gxp acting funny

    So I just put on a 3" downpipe and the engine light came on. I had the guy who did my tune turn off the CEL and now my car is acting very strange. While driving it shifts very hard, slow and hesitant shifts from 1st to second and from second to third. Hard enough to jerk my head and body on normal acceleration. In addition to the hard shifting I can feel the engine is very underpowerd and doesn't get up and go like it did before he turned the CEL off. Then when I put it in park it idles very low and rough at about 600 rpms almost on the verge of stalling. When I push the gas to raise the idle there is no response from the throttle whatsoever it doesn't do anything at all. These symptoms all came right after he flashed the computer and took the CEL off. He didn't change anything besides the O2 sensor. He tried a few other things on his laptop and hp tuners but he couldn't figure it out. Is it the computer malfunctioning or possibly something else? Any information is greatly appreciated. My car is an 07 with about 120k

  2. #2
    Killa Bee Scottydoggs's Avatar
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    Default Re: Diagnostic help. Pcm issue? Other problem?. 07 gxp acting funny

    time to go back to your tuner.

    98 Buick Regal GS, F body brakes, Caddy STS wheels, tinted tails L36 bottom end, lightly ported heads, 1.95 roller rockers, headers, 2.8, FSIC, 42 lb injectors, a BrandonHall rebuilt trans, DHP tuned and AEM water/Meth injection https://goo.gl/gpV5kW

  3. #3
    Donating Users 91parkave's Avatar
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    Default Re: Diagnostic help. Pcm issue? Other problem?. 07 gxp acting funny

    Ask him to send you the tune file I'll look at it. 91parkave@gmail.com
    06 GXP | 222/227 cam/cartuning turbo kit on 8psi/meth/e85 coilovers/ still on stock trans at 130k

  4. #4
    GrandPrix Junkie SgtMarshal's Avatar
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    Default Re: Diagnostic help. Pcm issue? Other problem?. 07 gxp acting funny

    I have a 2008 GXP and it idles at 600 rpm. I also drive a 2008 Suburban with a 5.3 and it idles at 600 rpm. it is very typical for V8 vehicles. I would check for an exhaust leak since you just changed your downpipe, you may not have one, but with it is best to eliminate the simple stuff first. the hard shifting could easily be a tuning problem, but there might also be a transmission issue exacerbated by the tune. might be best just to put it back to stock.

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    Default Re: Diagnostic help. Pcm issue? Other problem?. 07 gxp acting funny

    I asked him to send it. Still haven't gotten anything

  6. #6
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    Default Re: Diagnostic help. Pcm issue? Other problem?. 07 gxp acting funny

    How would I go back to stock with the computer? Take it to a dealer?

  7. #7
    SE Level Member Monday's Avatar
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    Default Re: Diagnostic help. Pcm issue? Other problem?. 07 gxp acting funny

    Any tuner should have taken a copy of stock before modifying your tune

  8. #8
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    Default Re: Diagnostic help. Pcm issue? Other problem?. 07 gxp acting funny

    Quote Originally Posted by 91parkave View Post
    Ask him to send you the tune file I'll look at it. 91parkave@gmail.com
    Sent the tune file. Let me know what you find out. Thanks

  9. #9
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    Default Re: Diagnostic help. Pcm issue? Other problem?. 07 gxp acting funny

    Get a chance to look at it yet?

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