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Misfire @ Idle

This is a discussion on Misfire @ Idle within the Computer & Tuning forums, part of the LSx Technical Help Section category; Ever since I installed my cam i noticed that it would misfire only at idle, scanned it and came up ...

  1. #1
    Member Flobeast385's Avatar
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    Pewter
    1999 TA M6

    Misfire @ Idle

    Ever since I installed my cam i noticed that it would misfire only at idle, scanned it and came up with a P0300 Multiple Misfire. Looking at the misfire graph all cylinders were misfiring at idle but while accel. there was not even 1 misfire. I am currently on stock tune and was wondering if the cam could be causing the misfire at idle or would i have another problem. I have changed plugs, wires, checked compression, fuel pressure and all are good. Any help appreciated.
    99 Trans Am M6
    SLP lid/FRA/TBB/Comp 224/224 581/581 112LSA
    Comp 918s/Comp PRs/Hedman TorkStep LTs
    Custom Y/Exhaust/Pro 5.0

  2. #2
    SUPREME member-oderator oneBADDz's Avatar
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    Custom Slate Blue
    99 B4C

    I've been reading up alot on cams lately, otherwise I wouldn't know what to tell you, lol. You aren't misfiring, until you get a tune you will get that code randomly. The cam writeup on ls1howto.com says not to worry about it, it just comes with putting a bigger cam in an LS1

  3. #3
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    The pcm mis-interpretates the lope caused by your cam as a misfire.

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    Member Flobeast385's Avatar
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    I figured that it was the cam because it is just doing it at idle and a code did not set until the install. I am getting it tuned very soon and hopefully that will take care of it. I also talked to Bryan Herter at pcmforless.com and he said that an average to large size cam would do that to the LS1 especially with a 112LSA. Haveing that said what do you guys think about a mailorder tune from pcmforless. Bryan the programmer said he has the same cam in his vette and could deffinitly get some power out of mine. The reason i am thinking of mailorder from his is because there is nowhere close that does dyno tunes and i am going to go with more cubes in the near future.

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    Member Flobeast385's Avatar
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    1999 TA M6

    Thanks for the replies

  6. #6
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    There has to be someone in NC that can tune HPtuner. Check out your regional forums section on here.

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    Member silverTA2002's Avatar
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    silver
    2002 Pontiac Trans Am

    Happened to me too. Totally normal.

    You can delete the code (not recommended in case of REAL misfire) or you can make the engine less sensitive to misfires at low rpm regions.
    2002 Trans Am 6sp, SLP lid, Holley filter, Shaner S3 TB, Jet Hot long tubes and cats, FRA, HP tuners, Hotchkis STB and LCAs. TEA stage 1.5 5.3 heads, Comp 220/224 114 +2, UMI Boxed SFCs, Edelbrock PHR. Moser 9" 4.11 gears.

    **FOR SALE**: http://www.ls1.com/forums/f38/fs-02-silver-t-heads-cam-headers-9-fl-60478/

  8. #8
    Member Flobeast385's Avatar
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    How would you go about making the engine less sensitive to misfires? I just need the light to stay off until i get it inspected, do you think raising the idle would help out for right now?

  9. #9
    SOM BTCH
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    SOM
    2002 Chevrolet Camaro Z28

    What software are you using to tune with?

    You need to locate the misfire detection at idle table and adjust those values.

  10. #10
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    Silver/Black
    2002 Camaro SS Cnvt

    Misfire detection is dummied out at higher RPM and MAP
    and only really "live" at idle and low cruise. You can play
    with the thresholds to just barely make it go away, if
    you have time to spend. Otherwise you can just shoot
    it for barking all night.

    Not to say some of it couldn't be related to the basic
    state of tune, but anything that increases crank jerk
    (lighter rotating components, imbalances, cam) is
    going to increase the ripple and probably outside the
    stock "normal range".

    At least one of the mods on HPTuners' 'board is NC
    based.

  11. #11
    Junior Member CM Hamrick's Avatar
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    White
    2001 Silverado SWB S/S

    I installed a 218/228 duration @ 50 cam in my truck and had the same problem. I use HP Tuners to do my own programming, It works great.

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