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Thread: ls1 lacking power when hot

  1. #1
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    Dec 2014
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    ls1 lacking power when hot

    Hi I'm new to tuning, however I have a vx holden commodre ls1 manaul, mafless, full exhaust and camshaft. I have this problem that when it gets to operating temp, it loses all power because its lean. Ive noticed through the log that map sensor reading is low when this happens. tps 96% , timing 32' and no knock retard, inj pulse 8ms which is too low and map 59kpa again too low. When vehicle is running well the map would be closer to 90kpa and inj pulse 13ms. any ideas what cause cause this would be helpful ? I have tried another map sensor, checked wiring, earths points all ok. Could a poor spark through faulty coils, crank or cam shaft sensor cause this ? Cheers

  2. #2
    What does the MAP sensor read with key on and engine off? It should read atmospheric pressure and if it does and you're actually dropping to 59kPa (not just a MAP sensor issue) at WOT, then there must be a significant restriction like throttle blade not fully open or some other restriction. A log would be useful showing MAP, TPS, Advance, O2 voltage or WB preferably (or both), InjPW, CommAFR and so on.

  3. #3
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    I found when hot the map sensor reading with engine off ig on to be 63kpa and approx 2.3v however the actual voltage at the pcm is 4.85 v I suspect a pcm fault. your ideas please ??

  4. #4
    Wiring, earth issue, or sensor itself would be the areas I'd check first. The PCMs are quite robust, but it's an easy variable to rule out.

  5. #5
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    Dec 2014
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    map sensor replaced, continuity and resistiance checks of map sensor wiring ok, pcm earth points and powers checked and terminals soldered. Also when checking the the map sensor voltage am i back probing the pcm and using the pcm earth points. I've also checked the map sensor configuration in hp tuners diag/airflow screen looks right map sensor linear 94kpa and offset 10kpa ? Is there any thing else in the software that could cause this ?

  6. #6
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    Post your tune and log file

  7. #7
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    Dec 2014
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    tune and log file


  8. #8
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    Dec 2014
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    I'm going to try another pcm, Are there certain pcms the will or wont be compatiable from other commodore ls1 manauls ? Can they be linked using vcm suite or made to work if so how ? Cheers