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Thread: Is it possible for a 98 pcm to "lose" a tune

  1. #1
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    Is it possible for a 98 pcm to "lose" a tune

    Sorry if this is in the wrong section, but as the title states is it possible for the pcm to lose a tune? I had my car tuned last year and it ran awesome for the first day, but literally overnight the shift points dropped from 6700rpm to 5800rpm and the rev limiter dropped from 7200rpm to 6700rpm and the car felt like it lost a lot of power. The only change I made after the tune was I pulled the abs fused as I was advised to do so by the tuner since the car has 26s up front and 28s in the rear. Is there a simple fix for this or do I need to get the car totally retuned?
    On a side note just yesterday the car had a PO118 code and I found that the temp sensor and plug is fried.

    Thanks in advance

  2. #2
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    Bill@HPTuners's Avatar
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    No it cannot. Once the tune is in there its in there.
    It doesn't have to be perfect, it just needs to be done in two weeks...

    A wise man once said "google it"

  3. #3
    You set the tune by the window sill too long, Damn neighborhood cats must have got it

  4. #4
    Senior Tuner mbray01's Avatar
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    check your fuel pressure, shift points dropping and loosing power sounds like low fuel rail pressure, and fuel trims going through the roof.
    Michael Bray
    Rusty Knuckle Garage
    Slidell, Louisiana
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  5. #5
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    A tune isn't on top of a stock tune...it's flash memory, and the tune replaces the old numbers with the new ones...they're there until someone replaces them again, OR the memory chips fail...they can't revert back to old numbers though.

    Quote Originally Posted by mbray01 View Post
    check your fuel pressure, shift points dropping and loosing power sounds like low fuel rail pressure, and fuel trims going through the roof.
    Agreed. Calculations getting all messed up from fuel trims going nuts. Change the fuel filter and make sure the pump is ok. I bet a lot of problems will go away.
    2010 Camaro SS M6. Stock Bottom End, Heads/Cam/Intake/Headers/Exhaust.
    2005 Silverado RCSB. Forged 370 LQ9/Borg-Forced Inductions T6 S484/Jake's Stage 4 4L80E with D3 Brake/4WD.
    2023 Durango Hellcat

  6. #6
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    Ok I will start with changing out the filter and go from there. Should I check the fuel pressure at the rails? The car has a new racetronix pump with hot wire kit so hopefully I don't need a new pump. Thank you very much I will report back with what happens after I swap the filter

  7. #7
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    Quote Originally Posted by Godspeed798 View Post
    Ok I will start with changing out the filter and go from there. Should I check the fuel pressure at the rails? The car has a new racetronix pump with hot wire kit so hopefully I don't need a new pump. Thank you very much I will report back with what happens after I swap the filter
    Pressure might be too high also...you want to see 58 PSI at the rails.
    2010 Camaro SS M6. Stock Bottom End, Heads/Cam/Intake/Headers/Exhaust.
    2005 Silverado RCSB. Forged 370 LQ9/Borg-Forced Inductions T6 S484/Jake's Stage 4 4L80E with D3 Brake/4WD.
    2023 Durango Hellcat

  8. #8
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    What would cause high fuel pressure at the rails? Also my plugs look like the car is running lean

  9. #9
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    Ok I checked the fuel pressure at the rail. When I key the ignition on it reads 50psi when I start the car it's hits 62psi and will stay steady at 62 at all RPMs. The car does not struggle to start or hunt for idle. Why would my fuel preassure be so high? It needs to be at 58psi right

  10. #10
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    62 isn't really high at all...the difference from that to 58 is minimal.
    2010 Camaro SS M6. Stock Bottom End, Heads/Cam/Intake/Headers/Exhaust.
    2005 Silverado RCSB. Forged 370 LQ9/Borg-Forced Inductions T6 S484/Jake's Stage 4 4L80E with D3 Brake/4WD.
    2023 Durango Hellcat

  11. #11
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    Changed my fuel filter and burnt ect sensor and its still the same. Would it make a difference that my car was tuned about a 3000ft lower altitude?

  12. #12
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    Could a bad iat sensor cause these problems? I'm running out of ideas.