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Thread: 05 Grand Prix tuning question

  1. 05-04-2010 #1
    blwn3800
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    05 Grand Prix tuning question

    Hey guys. I just got Hptuners so im still very new at this. I've been reading and learning alot and I'm trying to tune my grand prix but have a question about something thats been perplexing me. When i scan my vehicle the narowband o2 sensor alternates between 40mv to 750mv and averages somewhere in the 300mv range, but my stft's are constantly negative which would mean its pulling fuel correct?. Now my understanding is that 300mv is extremely lean, the lower the leaner, but the pcm keeps pulling fuel. What would cause the O2 sensor to be reading lean and for the pcm to keep pulling fuel?. What am i missing here? I dont have a wideband yet, I'm just trying to get the idle and cruise acceptable for now, but no matter what i do it runs like crap(missfires and shakes). Please help

    05 Grand prix GTP comp g.-180*t-stat, headers- cated DP, xp cam, CAI, stock 3.8 pulley.
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  2. 05-05-2010 #2
    MMGT1
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    Would this be an "idle" issue? I know you are new, so before someone jumps all over you here, post a scan and and your current file. Its really hard to see what you have going on without the scan and the current VCM files you are using.
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  3. 05-05-2010 #3
    MMGT1
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    These v6s are about the hardest things in the dam world to get right man. After spending a couple of years tuning my v6 the rest of them out there are easy. Took me 3 years to get my v6 even close, did the TA in 4 hours... lol

    I will warn you straight up, we have to use some very "unconventional" methods as there are a lot of tables not available to the v6 community
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  4. 05-05-2010 #4
    blwn3800
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    MMGT. Thanks for replying. Man tell me about it, I read all these tuning guides but they always mention tables i dont even have. And i figured it would take "unconventional" methods like you said.

    Here's the most recent scan, it is just the car at idle. I have closed loop disabled until 75* ECT.
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  5. 05-06-2010 #5
    MMGT1
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    Scratch that whole message. Have you checked those headers for any leaks? Leaks around the bung for the NB WB sensor?
    Last edited by MMGT1; 05-06-2010 at 07:31 PM.
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  6. 05-07-2010 #6
    blwn3800
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    You got it! haha There was a leak in the flex. I had a new flex welded in and now everything is reading properly. Thanks for the help man.
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  7. 05-25-2010 #7
    MMGT1
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    Nice, I had my headers installed originally without any gaskets, and had 0 issues. I put in a new built block a couple of months ago and my fuel went nuts. The gaskets were leaking at two of the flanges, and my scans looked much like yours did there. Glad it helped man
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