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How's this for a problem

Discussion in 'The Garage' started by SoonerBob, Aug 12, 2006.

  1. SoonerBob

    SoonerBob Registered Member

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    OK, so last month I was coming back from the lake when my K5 started running like crap. I had to leave it at a shop and have someone come get me because it wouldnt go faster than 30mph on the interstate. It sounded like it wasn't getting enough fuel and wouldn't even rev up into the higher rpm's. Luckily for me, there was a shop right there on that exit so I left the truck there and called the guy the next day to see if he could fix it. Well, 1 month and a rebuilt throttle body, new fuel filter, fuel pump, and a new computer later it still does the same thing. He told me that sometimes it will run just fine then other times it will go back to running terrible. He also checked the fuel lines, checked all the electronics on it, etc... and changed what he could and it still doesn't run right.

    So-

    Does anyone know what could be the problem? I'm going to pick it up this weekend and after that I dont know what to do with it. I know it can be fixed, but I need to know what to fix first. Thanks in advance
     
  2. southernspeed

    southernspeed 1/2 ton status GMOTM Winner

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    I HATE so called mechanics who just replace stuff until they find the right thing and then give you a massive bill. If it was running that bad surely it threw a code or 10?
    It could be a spark problem, air leak, timing........
    I really hope he doesn't charge you for all the stuff he's replaced but somehow I think he will. I'd phone him and tell him you're getting it taken elsewhere as he obviously hasn't got a clue.
    If it sounds like I'm pissed, then I am. This is what gives shops a bad name. Your paying for a shops expertise to diagnose a problem, not rebuild your rig until it's fixed.
    Sorry to rant. Good luck.
     
  3. 4xcrazy

    4xcrazy 3/4 ton status

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    ditto
     
  4. SoonerBob

    SoonerBob Registered Member

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    the only thing he's charged me for is the pressure regulator valve rebuild kit, other than that he didnt charge me for anything.
     
  5. SoonerBob

    SoonerBob Registered Member

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    but i told him to do that, since i dont have a clue anymore as to what could be the problem
     
  6. Chevy305

    Chevy305 6 Lug 14bsf Status Premium Member GMOTM Winner

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    put on new plugs and wires. I could very well be a faulty plug wire
     
  7. blazinzuk

    blazinzuk Buzzbox voodoo Premium Member GMOTM Winner

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    Bad ground on the computer, very hard to figure out I don't even know how to fix it but I have had 2 cars that had similar problems and thats what they both were
     
  8. Kyle Strong

    Kyle Strong 1/2 ton status

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    I had a problem like that with mine, but it would spit oil and not go above 30 mph. I just found out that I have 70% blowby, and the pcv system coudn't remove all of the pressure. So now I need to replace the rings or go 454 :D And as far as the shops go, I hate them too. Just glad to hear that he hasn't charged you for anything you didn't ask for.
     
  9. fabjunkie

    fabjunkie 1/2 ton status

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    A plug wire isn't going to cause you not to go over 30mph. It will just give you a bad miss. I'm guessing the catalytic converter. If it's clogged, the motor wont rev, and you sure aren't going anywhere fast. I had this happen in my old Ram and I was driving it one day, after it sitting and not being able to figure out what was wrong, because I didn't have any other way to get to the store. When I pulled out of the parking lot, it made a huge boom, and took off like a bat out of hell. I guess it finally had enough to blow the crap out of the cat.
     
  10. beater_k20

    beater_k20 Banned

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    Translation: I have no idea what it is either, throw more parts at it, maybe it will fix the problem.
     
  11. dyeager535

    dyeager535 1 ton status Premium Member

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    Need more for symptoms, or is that the ONLY one?

    Codes, visual inspection done, etc?
     
  12. Russell

    Russell LB7 Tahoe Status Premium Member GMOTM Winner

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    Try setting your timing. Make sure that the EST (Electronic Spark Timing) bypass gets unplugged, and that you set it to about 5 - 6 degrees advanced. Stock is 0, but the stock timing is very convservative, and by adding 5 - 6 degrees base timing, you only pick up power. If you get detonation, the knock sensor retards the timing automatically. EST bypass is found up behind the cover where the fuel pump relay / fuse & power distribution block is located. Its a single tan / black wire connector.

    Next make sure that your EST module is working properly as well. If you don't have any spark advance, you don't go anywhere fast. EST module is found just to the left of the throttlebody (pass side of the engine) and is the big flat square module.

    Then check your fuel pressure. If your fuel pump isn't providing between 12 - 15 PSI of fuel pressure to the injectors, you won't be going anywhere fast at all.

    Next check your grounds. A poor ground will equal an engine that doesn't run properly. The grounds for the ECM are found attached to the thermostat housing stud, and one down near the back of the intake where the 02 sensor is. You need to make sure you run the tan O2 sensor ground to the head / manifold that has the 02 sensor in it, and you also need to make sure that all the other grounds are clean. If you don't have bare metal showing, whip out the sandpaper, and make them shiny.

    Finally, make sure that your CTS (Coolant Temp Sensor) is reading accurately, it will pour craploads of fuel into the engine if it is reading falsely cold, or falsely hot, and make your truck run a bit like a truck that has the choke stuck closed on the carb.

    Of course, the shop should have a scanner and be able to check all the sensory stuff at a quick glance, and they'd better have a fuel pressure gauge. If they don't then, you need to be taking the truck to another shop anyways :)

    TBI is has no black magic involved. Its a very simple system, and so long as everything is reporting reasonable signals, your engine will run.
     
  13. southernspeed

    southernspeed 1/2 ton status GMOTM Winner

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    "Well, 1 month and a rebuilt throttle body, new fuel filter, fuel pump, and a new computer later it still does the same thing." ???

    As has been mentioned, a collapsed cat can give very similar symptons.
     
  14. SoonerBob

    SoonerBob Registered Member

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    Um, it doesn't exactly have cats. They were missing when I bought the truck:o and here in OK there is no inspection or emissions testing :laugh: BUT - I did recently get 2 new Magnaflows put on it and these problems started after those were installed.

    The guy that worked on it said that it had good compression, it was getting plenty of fuel and whatnot, and he checked all the electronics. Oh, and another thing - when it gets low on gas it starts to run better and better, then when I fill it up it goes back to running absolutely horrible and not getting over 20mph.
     
  15. SoonerBob

    SoonerBob Registered Member

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    and I must add that when I press on the gas it just bogs down and doesnt do anything, then when I let my foot off the pedal the rpms surge for a split second and it gets power.
     
  16. RaisedK5

    RaisedK5 1/2 ton status

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    IF thats the case then your gas tank may not be venting properly. Do you still have the charcoal canister on the core support or did that "disappear" too?? I'm betting that the fuel tank is not vented correctly and not allowing fuel to leave the tank, thus starving the motor. try removing the gas cap and seeing if it runs better.
     
  17. Smokin'Joe

    Smokin'Joe Registered Member

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    Have you checked your o2 sensor? A fouled o2 sensor could cause a loss in fuel mileage and power. Also check your ignition module. Otherwise I,m clueless...
     
  18. Russell

    Russell LB7 Tahoe Status Premium Member GMOTM Winner

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    I still say check your timing!
     
  19. roadnotca

    roadnotca 3/4 ton status

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    X2 on gas cap.:D
     
  20. SoonerBob

    SoonerBob Registered Member

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    i did run it without the gas cap and if at all possible it ran worse.
     

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