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Symptoms...

This is a discussion on Symptoms... within the Internal Engine forums, part of the LSx Technical Help Section category; New 402 iron block Patriot Stage III LS6 heads TSP Giant cam --- 248/254 629/622 113 FAST LSx 90/90 Morel ...

  1. #1
    Slow'er'Ass Mr. Luos's Avatar
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    Red Tint Jewelcoat
    2008 Trailblazer SS

    Symptoms...

    New 402 iron block
    Patriot Stage III LS6 heads
    TSP Giant cam --- 248/254 629/622 113
    FAST LSx 90/90
    Morel lifters, stock rockers

    Car runs.
    Backfires at idle.
    Hesitates terribly in lower RPM's.
    Not a strong as it should be, but runs smooth above 3500 RPM's.
    Lower RPM's...it has shot fire when it hesitates.
    Replaced O2's, cleaned MAF, reset computer. Same issues.

    New problem....stainless headers started glowing after about 3 minutes at 1300 RPM's.

    Ideas??

  2. #2
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    Sounds like a timing problem, have you done your full blown tune?
    If your headers are glowing I would say it is deffentaly a timing problem.

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    Space Cadet RainMan's Avatar
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    2002 WS6, '08 G8 GT

    Exhaust or Intake Backfire?
    Black Sooty exhaust?
    How is the idle?, other than the lope of that huge cam?

    Lower RPM's...it has shot fire when it hesitates
    What do you mean by, shot fire? A "POP" through the intake? Late Timing.

    Do you have an off idle stumble when you get on the gas? Late Timing

    SES codes?

    What's your fuel pressure at idle?

    Glowing headers? Excessive heat, indicates fuel burning in headers.
    An rich condition with late ignition timing, so far without more info??

    Sounds like a bad tune;
    Late ignition timing,
    Very rich.
    or
    Crank Sensor bad or not properly positioned, hooked up

    Stupid Question I have to ask??? You did get it tuned after you put he engine in right?

  4. #4
    Slow'er'Ass Mr. Luos's Avatar
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    There is a base tune on it. Done by a shop owner that knows his stuff.
    SES light is on...not sure which code right now. I had reset the computer.

    The only one I had seen previous was P0300. Expecting that one though.
    What about WAY lean....would that cause red hot headers and all the stumbling?
    I believe I may have located a large vacuum leak....I don't think my intake is sitting down on the heads all the way. I messed up on the install of the valley cover bolts. I put the stock LS1 ones back on.
    Gonna pull the intake off tomorrow and hope to god it isn't cracked.

    Backfire is exhaust.
    Hasn't ran long enough to determine if the exhaust is sooty...
    Idle seems okay....does kill itself off sometimes though.
    Crank sensor....that would have thrown a code if it wasn't learned right?
    Probably gonna do the relearn anyways.
    2008 Trailblazer SS
    Yank PTB3600, Kooks 1 7/8" LT's, 4" intake, E-fans, Magnaflow, Sonnax kit, tranny cooler, tune.
    Lowered, HID's, tinted.

    1999 Pontiac Trans Am WS.6 #1747 SOLD
    531.1 RWHP 481.3 FT/Pounds all motor.

  5. #5
    Space Cadet RainMan's Avatar
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    What about WAY lean....would that cause red hot headers and all the stumbling
    Actually no, that is one of those "Wives Tales"! I found a site that explains; http://racingarticles.com/article_racing-56.html

    #7 is about the Glowing Headers, I especially like #8! I've always been reluctant to recommend a very aggressive Cam, and/or monster heads for anything less than all out racing.

  6. #6
    Slow'er'Ass Mr. Luos's Avatar
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    Good read.
    Thanks!

  7. #7
    Tech Junkie hammertime's Avatar
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    Quote Originally Posted by RainMan
    Actually no, that is one of those "Wives Tales"! I found a site that explains; http://racingarticles.com/article_racing-56.html
    LMAO @ #10!!

  8. #8
    Senior Member Street Lethal's Avatar
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    Quote Originally Posted by Mr. Luos
    What about WAY lean... would that cause red hot headers?
    No, you're definitely pig rich. Did you pull you're spark plugs to inspect yet? As previously asked, what is you're fuel pressure set at?

    Quote Originally Posted by Mr. Luos
    I believe I may have located a large vacuum leak. I don't think my intake is sitting down on the heads all the way. I messed up on the install of the valley cover bolts. I put the stock LS1 ones back on.
    What lead you to this assumption? Did you try and spray some injector cleaner aound the base of the intake during idle? If so, did RPM increase any?

    Edit: Spelling
    Last edited by Street Lethal; 02-04-2006 at 06:31 AM.

  9. #9
    Slow'er'Ass Mr. Luos's Avatar
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    Quote Originally Posted by Street Lethal
    What lead you to this assumption? Did you try and spray some injector cleaner aound the base of the intake during idle? If so, did RPM increase any?
    FAST LSx doesn't fit over the stock LS1 valley cover bolts.
    I have the stock LS1 valley cover bolts on there.
    Going to swap those out today and see if that helps.
    Talking with the shop that built the motor yesterday, and he seemed to think it was vacuum related. He started asking my some questions...and the valley cover bolts was one of them.

  10. #10
    Senior Member Street Lethal's Avatar
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    Quote Originally Posted by Mr. Luos
    FAST LSx doesn't fit over the stock LS1 valley cover bolts. I have the stock LS1 valley cover bolts on there.
    I would still at least spray some Carb/FI cleaner around the base during idle.... just to underline it being vacuum related. Did you get a chance to pull the plugs yet?

    BTW, that's one hell of a cam you selected. Do you know the tuner well? Credible?

  11. #11
    Slow'er'Ass Mr. Luos's Avatar
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    Yes he is. He has been tuning some of the stronger cars in Colorado.

    I planned on getting out there today and checking on a couple little things. Plugs, the possible vacuum leak, etc....
    The shop that built the motor seemed to think it was going way lean. But it acts way rich.
    I really need to just eat the cost of a wideband.

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