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Engine surge/flat spot 2k-3k rpm

This is a discussion on Engine surge/flat spot 2k-3k rpm within the General Help forums, part of the LSx Technical Help Section category; My '99 Firehawk, with 130K miles, has developed a "stumble", "flat spot" in the 2k-3k rpm range during moderate acceleration. ...

  1. #1
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    navy blue metalic
    199 Firehawk

    Unhappy Engine surge/flat spot 2k-3k rpm

    My '99 Firehawk, with 130K miles, has developed a "stumble", "flat spot" in the 2k-3k rpm range during moderate acceleration. My plugs and wires were changed at 100K miles, the OBD is not registering any codes. When not under load I cannot hear or feel this, but it is quite noticeable when the engine is under moderate load. Where should I be looking?

  2. #2
    That guy thearborbarber's Avatar
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    1991 Suburban

    I would change the fuel filter and clean the MAF.

  3. #3
    my ws6 eats rice gokillyourself's Avatar
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    sexy
    1999 trans am ws6

    i have the same flat spot but mine is under normal acceleration, it picks up speed like normal then a big sudden loss of horse power, i wrote about it in a new thread in the "general info" its called "don't run like she used to", maybe you can some clues there and if you find something out please pass the info along in my thread

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    TunedbyFrost.com Tuner Frost's Avatar
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    I see more and more failed MAFs every week.. They don't code either they just report crazy low airflow values and the car wants to run way lean. They all have very high + long term trims values.

  5. #5
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    navy blue metalic
    199 Firehawk

    Surge/loss of power

    I recently cleaned the MAF.
    If it is the MAF, any way to diagnose it?

  6. #6
    Moderator 35th-ANV-SS's Avatar
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    Check your other posting about the MAF checking.

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    TunedbyFrost.com Tuner Frost's Avatar
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    Quote Originally Posted by bcorwin View Post
    I recently cleaned the MAF.
    If it is the MAF, any way to diagnose it?
    I look at the frequency they report in different areas and just know whent hey are low... if you have large positive LTFTs then it could be suspect, they will accompany it.

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    1999 Camaro Z28

    Surge/flat spot fixed

    I have had this problem for quite a while. Cleaned MAF serveral times, new plugs, wires, o2 sensors. Still there. Just for the hell of it I replaced the throttle position sensor since it is only $40 and WOW what a difference. Smooth as butter going up and down through the rpms range.

    Try it!

    99 Camaro Z28 107,000 miles.

  9. #9
    my ws6 eats rice gokillyourself's Avatar
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    sexy
    1999 trans am ws6

    Quote Originally Posted by olendorf View Post
    I have had this problem for quite a while. Cleaned MAF serveral times, new plugs, wires, o2 sensors. Still there. Just for the hell of it I replaced the throttle position sensor since it is only $40 and WOW what a difference. Smooth as butter going up and down through the rpms range.

    Try it!

    99 Camaro Z28 107,000 miles.
    i was thinking of unplugging it to see if it makes a difference, it it acts better then i am going to replace the tps

  10. #10
    TunedbyFrost.com Tuner Frost's Avatar
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    If you unplug it, drive the car EASY. There will be no enrichment available for moderate to heavy throttle. I'm not sure this could prove whether or not one is bad though...

  11. #11
    my ws6 eats rice gokillyourself's Avatar
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    sexy
    1999 trans am ws6

    Quote Originally Posted by Frost View Post
    If you unplug it, drive the car EASY. There will be no enrichment available for moderate to heavy throttle. I'm not sure this could prove whether or not one is bad though...
    thanks frost but i am running out of ideas, you can see what i have done so far in the general help called "she don't run like she used to"

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    can the tps be cleaned?

    i started a post titled hesitation under load'. sounds afwully similar to my symptoms.

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    Quote Originally Posted by 5abivt View Post
    can the tps be cleaned?

    i started a post titled hesitation under load'. sounds afwully similar to my symptoms.
    I first took mine apart to look at it to see if if needed cleaning. It looked ok but I cleaned it anyway with electrical cleaner. Be very careful with the metal fingers that press along the barrel. It isn't one metal finger but lots of very, very fine strands and they are easily bent and ruined. After I cleaned mine and put it back together it ran the same. I'd say don't waste your time. It is too easy to ruin it and it probably needs to be replaced anyway.

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    The suggesion of a bad tps does make sense thinking about my cars symptoms. Under different throttle openings the timing would be drastically different. Interesting... going to see how much one is tomorrow and try to swap it with the fuel filter at once.

  15. #15
    my ws6 eats rice gokillyourself's Avatar
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    sexy
    1999 trans am ws6

    Quote Originally Posted by 5abivt View Post
    The suggesion of a bad tps does make sense thinking about my cars symptoms. Under different throttle openings the timing would be drastically different. Interesting... going to see how much one is tomorrow and try to swap it with the fuel filter at once.

    i am going to check out the tps too and i am also thinking of changing the o2 sensors

  16. #16
    TunedbyFrost.com Tuner Frost's Avatar
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    Quote Originally Posted by gokillyourself View Post
    i am going to check out the tps too and i am also thinking of changing the o2 sensors
    Where are you located in VA?

  17. #17
    my ws6 eats rice gokillyourself's Avatar
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    1999 trans am ws6

    Quote Originally Posted by Frost View Post
    Where are you located in VA?
    i'm in galax virginia

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