Only 75% Power When Hot

Discussion in 'SN95 4.6L Mustang Tech' started by Calebnc302, Jun 20, 2013.


  1. Calebnc302

    Calebnc302 New Member

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    My 03 gt 5spd with nitto 555s will throw u in the back seat at WOT after a easy 2 or3 minute warmup to about half way to operating temp. But once it gets hot then it has this lack of accelerating like it stays in lower Rpms for a longer period. It's like it lost 20% power. I have replaced fuel filter, plugs, air filter, cleaned maf. It runs good, no sputter, or cutting out, it just loses acceleration. Also no cel or codes. Could the heat affect it this much? If so, what can help this?
  2. trinity_gt

    trinity_gt Advanced Member

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    Do you have an aftermarket intake on the car? If so, what type?

    Theory: A cone filter open to the engine bay is sucking hot, underhood air. High IATs result in less dense air and retarded timing to prevent detonation.


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  3. Calebnc302

    Calebnc302 New Member

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    Car is 100% stock accept for o/r x and knn air filter. So is this normal for an all stock gt on an 85' day?
  4. trinity_gt

    trinity_gt Advanced Member

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    Airbox snorkel/silencer removed or still intact?
  5. Calebnc302

    Calebnc302 New Member

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    It's there.
  6. Calebnc302

    Calebnc302 New Member

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    Any help people? Is this normal?
  7. Gary Ugarek

    Gary Ugarek Member

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    Cars love cold air. My 2000 GT, with 108k on the clock, in the morning when it is about 65 outside, runs like a raped ape. When I get off work and it is 90, I feel s power loss, I wouldn't say 25%, but there is a small loss for me.
  8. Calebnc302

    Calebnc302 New Member

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    Yeah I'm pretty sure I'm losing more than I should be when it's hot. I'm prolly exaggerating with 25% but its definitely noticeable loss of acceleration. What could be wrong?
  9. Calebnc302

    Calebnc302 New Member

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    Hey Trinity gt my car does not have the air silencer/snorkel. I was mistaken about this. Do u think this could be my problem on a warm day sucking in more heat? Like I swear it feels like I lose 20hp maybe more when it's hot.
  10. trinity_gt

    trinity_gt Advanced Member

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    Without the snorkel the engine is pulling air from the under-hood environment through the big hole in the side of the airbox. If you have high under-hood temperatures you're losing charge density and the PCM is probably pulling spark timing. I think the factory tune is pretty mild when it comes to timing and IATs because the 2V lacks knock sensors and is factory-rated to run with 87-octane fuel.

    See what you can do to get cool air from the fenderwell and see if that makes a difference.
  11. Calebnc302

    Calebnc302 New Member

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    Ok will try that next. Thanks for the help
  12. Mustang5L5

    Mustang5L5 Car used in adult film "Highway Gangbang-InDaButt" SN Certified Technician Founding Member

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    My 03GT i bought brandy new was a dog when it was hot. Toss the A/C on and it felt completely gutless. I've never had a car with as much power loss when it was 90+ degrees out as that one.
  13. Calebnc302

    Calebnc302 New Member

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    Haha that's good to know that there's nothing major wrong then. I guess it's just the 4.6 nature
  14. PULMEOVR

    PULMEOVR I need a bigger E-Penis.

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    For what it's worth, mine also feels like a dog when it's hot out. I think thats just the nature of these engines. In the nice cold air it feels much much faster.
  15. Calebnc302

    Calebnc302 New Member

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    Yeah I guess so. At first I thought maybe something was wrong but after hearing other people say the same I guess it's just the it is.
  16. runningONfumes

    runningONfumes Member

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    I might be misunderstanding what you're reffering to... do you have problems at car op temps or outside weather temps? Don't rule out internal problems if its not extreamly hot outside. Last summer at the track temps were over 100 degrees and i had no performance issues. Do this test... next time youre on the freeway and you feel your car is doing what you explained above, once you've shifted into 3rd and you're at wot... back off the throttle just a touch...say 3/4 throttle. If your rpm jump up in any way have your ride checked for compression and valve accuracy.
  17. COramprat

    COramprat Drone Driver Mod Dude

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    Hot outside temps. My car is a brick in hot weather.
  18. Calebnc302

    Calebnc302 New Member

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    Yes it is the hot temps cuz these last few cool days have been great
  19. runningONfumes

    runningONfumes Member

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    Good to hear that bro!

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