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454 falling on its face

Discussion in 'The Garage' started by NoReGrEtS, Oct 30, 2006.

  1. NoReGrEtS

    NoReGrEtS 1/2 ton status

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    the 454tbi in my suburban is running funny.It will ideal fine but if your driving it, give it half throttle it falls on its face and almost dies. with it parked it revs just fine only seems to do it under load and at half throttle.
    I have changed the plugs,cap,rotor. I'm going to clean the K&N.
    any thought on what it could be?
    I was searching and didn't come up with any thing



    Thanks Shawn
     
  2. NoReGrEtS

    NoReGrEtS 1/2 ton status

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    changed the air filter and it helped a little but still did it
     
  3. Drey

    Drey 3/4 ton status

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    02 sensor? computer? any lights flashin at ya or anything?
     
  4. xpndbl3

    xpndbl3 1/2 ton status

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    how's the fuel pressure under load?
     
  5. bronc3buster842001

    bronc3buster842001 1/2 ton status

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    check the map sensor
     
  6. big dan

    big dan 1/2 ton status Premium Member

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    I dont know much about fi but what about the fuel filter?
     
  7. dhcomp

    dhcomp 3/4 ton status Premium Member

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    Fuel filter would probably be opposite symptoms....
     
  8. NoReGrEtS

    NoReGrEtS 1/2 ton status

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    no light flashing, it was only hesitating when cold a few month ago, I haven't driven it lately. I have to drive tomorrow so I hope it don't die.

    How do I go about checking the sensor's?


    Thanks Shawn
     
  9. sapper

    sapper 1/2 ton status GMOTM Winner

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    Have you checked the coil? mine did that a few years ago. hopefully that will help as they are cheap
     
  10. NoReGrEtS

    NoReGrEtS 1/2 ton status

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    forgot about this.

    I had the head lights on and was reving the motor, I was slowly building up the R,s to see if I could get it to do it and about3500 to 4000(dont have a tach) and the light dimed alot.
    I dont know if that has any thing to do with it or that was at the motors peak power sucking point?:confused:
     
  11. blazin_blazer

    blazin_blazer 1/2 ton status

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    just what i was thinking, but

    i had a buddy with a 91 1 ton burb that was doing the same thing, he changed fuel filter and no change...turned out to be cataylitic converter had something that would blow up like a flap covering the exhaust pipe to nearly nothing, making it fall on its face, we don't have a smog check here, but we pulled it off and it runs fine ever since. the exhaust shop actually showed us the problem after he had duals installed.
     
  12. NoReGrEtS

    NoReGrEtS 1/2 ton status

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    I will have to look in to that

    thanks Shawn
     
  13. Musclerodz

    Musclerodz 1/2 ton status

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    Most likely the cats. Sounds like the same thing that happened to me couple years ago and it was the cats on my '97 454 crew.

    Mike
     
  14. SchnorrCS

    SchnorrCS 1/2 ton status

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    Plugged cats is kinda what I was thinking....
     
  15. Thunder

    Thunder 3/4 ton status

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    Before you do anything..........Change your Fuel filter!!!!!!! Its cheap easy and will prolly solve your problem. If you have FI your filter should be changed once a year for bset prformance and MPG. But hell dont listen to me.... Spend a bunch of money replacing everything else first then find out its something simple...... Thats what most folks do.
     
  16. blazin_blazer

    blazin_blazer 1/2 ton status

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    worth the money

    i agree change filter 1st...if still haven problem check the cats!
     
  17. JEBSR

    JEBSR 1/2 ton status

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    I agree that it sounds like the cat(s), but don't just go replace it/them. Take it to an exhaust shop and have a backpressure test done or take the exhaust loose and drive it. Either of the two will tell you whether that is your problem or not.
     
  18. 89Burben

    89Burben Registered Member

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    i had the same problem with my 454 tbi, replaced everything! i mean everything, truck was down a whole summer:mad:

    it ended up being the little fuel filters under each injector. Both were spraying fine and fuel pressure was fine but when under a load or half to full throttle it was horrible. got to the point where it was backfiring through the tbi cuz it was so lean....

    i believe it has to do with the amount of ethanol in the gasoline today, its cleaning everyones tanksand fuel lines and clogging fuel filters. Many boats today with FI are having same issues with clogged fuel injectors and whatnot.

    CHange the main fuel filter and get a tbi rebuild kit, they are only 30 bucks and it will only help.:wink1:
     
  19. DavidB

    DavidB 1/2 ton status

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    Figger it out?
     
  20. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    Doubt it... they are chasing their ass.

    Half the replies are practitioners of "Guess and spend auto repair". Eventually they will replace enough expensive parts and accidentally fix the problem if he listens to them. The only thing I have heard here that makes any good sense is the filters and that's just some issues with lack of regular maintenance. Thunder and bronc is the only ones I respect for a decent reply.

    Yeah change the cats...guess what... if it needs cats it's because there is a pre existing problem so fix it first so you don't screw the new cat (if it actually needs one)

    I about guarantee this is vacuum leaks. Mine did similar and it was Vacuum line to the Map got hard and split where it wasn't visible on the back side of the TBI. I also had cracks in all the plastic lines AND a bad gasket under the TBI.

    Bet when it was running better it had a surge or a "chuggle" (term from manual).

    Course if you read the factory manual the fist thing it tells you to do is look for vacuum leaks for this complaint.


    I quote on diagnostics section 2-6 or the 1988 10-30 R-V-G-P lightduty service manual:

    Hesitation, Sag, Stumble

    In order right out of factory manual
    • Perform careful visual (physical) check as described at the start of section 2 (section 2:vacuum hose leaks, Air leaks at throttle body, ignition wires, poor electrical connections IN BOLD IT SAYS The importance of this step cannot be stressed to strongly-it can lead to correcting a problem without further checks and can save valuable time)
    • fuelpressur, water contamination, timing
    • fuel pump
    • tps
    • generator output
    • bad grounds (there are several up on the intake for TPS, injectors and Map
    • hei
    • egr
    First tool to use is a decent manual. You are chasing your ass if you start anywhere else. When mine screwed up I took 10 minutes to read the diagnostic and 10 minutes later I found that bad vacuum line. $30 at the parts store later I replaced ever questionable Vacuum line on the truck. truck never ran better.

    It's funny how the manual always starts with the practically free repair then works its way up to carefully testing each component to verify operation or failure before it says to replace. It start with not only the cheapest but the most common problem.

    Course if you listed to half the people here you would have just spent about $800 on parts and labor. I bet you can fix it for less then $20.
     
    Last edited: Dec 25, 2006

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