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runs terrible at high rpm's

Discussion in 'The Garage' started by SoonerBob, Jun 14, 2006.

  1. SoonerBob

    SoonerBob Registered Member

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    my 88 K5 with the 350 TBI runs fine at low rpms for street driving, but it runs absolutely terrible at high rpm's when i have to hammer it down. it cuts out and bogs down and I have almost zero accelerating power. what is going on and how do I fix it?? :( :confused:
     
  2. 1985_K5_Silverado

    1985_K5_Silverado 1/2 ton status

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    Could be a fuel delivery problem. Is the ECM tossing out any trouble codes?
     
  3. Wishbone

    Wishbone 1/2 ton status

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    Wonder if the spark plugs are getting enough spark at higher rpm's? Have you changed your plug wires in a while?
     
  4. Leper

    Leper 1/2 ton status

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    Many problems like yours are related to fuel delivery and/or spark. Possible causes: clogged fuel filter, sticking injectors, fuel pump going out, fouled plugs, bad wires, coil break down, worn cap, worn rotor, and I have even seen a dist come apart on the inside.
     
  5. loafer

    loafer 1/2 ton status

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    My old 88 TBI used to do this quite often; It was always a partially plugged fuel filter. For some reason I used to get a lot of dirt in my tank:D

    Sometimes the strainer on the fuel pickup in the tank gets plugged as well.

     
  6. SoonerBob

    SoonerBob Registered Member

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    the cap, rotor, wires and plugs were all replaced less than 2 years ago. the fuel filter was replaced a year ago but I guess I could double check these things. If none of that tells me what I need then I guess I can assume it's an injector or fuel pump problem. :mad: :mad: That doesn't make me too happy.
     
  7. loafer

    loafer 1/2 ton status

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    I used to have to replace my fuel filter every 6-8months. When you pull the fuel filter dump it out and see if you get any rust.

    What about the fuel pump?


     
  8. SoonerBob

    SoonerBob Registered Member

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    well i hate to admit it but i'm not all too familiar with where the fuel filter would be located
     
  9. steve_kibbe

    steve_kibbe 1/2 ton status

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    How about vacume advance?
     
  10. 88Silverado

    88Silverado 1/2 ton status

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    My 88 was doing the same thing last year. Ran fine at low speed but couldnt pass anything cuz it would just croak. It was the Fuel Filter. It didnt set any codes but when the filter gets plugged, it cant deliver the fuel it needs.

    The filter is located on the passenger side frame rail about mid-way back. Simple changeout.
     
  11. JEBSR

    JEBSR 1/2 ton status

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    I agree with the fuel filter opinions, however something that I have ran into is a clogged exhaust system causing the same symptoms. I would have the fuel pressure checked and if it is good have the exhaust back pressure checked.
     
  12. smokkey1

    smokkey1 1/2 ton status

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  13. Propayne

    Propayne Registered Member

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    for my own knowledge, why would back pressure be problem enough to cause this?
     
  14. diesel4me

    diesel4me 1 ton status Premium Member

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    It cant breathe!!...

    A restricted exhaust might not be noticeable at low speeds,but will limit how much air gets IN the motor at higher speeds and loads..if it cant get enough air/fuel mixture IN,it will run poorly,if at all...the exhaust "backs up" into the cylinder,and prevents fresh fuel and air from getting in if the exhaust is restricted..a restriction in the intake ,like a clogged air filter,will do much the same thing,only it makes it run too rich from lack of air...fuel cant ignite without air!..

    I'm hoping he doesn't have a cam lobe going flat..but that would likely cause backfiring thru the intake or exhaust at high revs....weak valve springs can cause missing at high speeds too..the valves "float" and cause missing...hopefully its just a clogged fuel filter or weak pump causing his woes..:crazy:
     
  15. 68MUDSTUD

    68MUDSTUD OCD with shiny things

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    my guess is that it would be the vaccuum advance because the springs in your Distributor (if its an HEI) will wear out and you will have to replace them... also it could be the arm or may just need to be tightened.
     
  16. JEBSR

    JEBSR 1/2 ton status

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    As far as the exhaust backpressure you take out your 02 sensor and install an exhaust pressure gauge (most exhaust shops have one) and start the truck up and get your answer.

    I would check the fuel pressure first though.
     

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