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My truck goes: "WHOMp WHOMp WHOMp.." help!

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by KRAZIE87K5, Nov 5, 2002.

  1. KRAZIE87K5

    KRAZIE87K5 1/2 ton status

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    My truck goes: \"WHOMp WHOMp WHOMp..\" help!

    Okay, for the first time after my recent trail run out to Potosi, Missouri I took the truck to work. The damn thing starts up and sounds like a top fuel dragster... you know the ones where you can hear the individual cylinders firing like BLAT BLAT BLAT BLAT BLAT... (you get the picture /forums/images/graemlins/tongue.gif) Which is very uncharacteristic of my engine, it NORMALLY idles smooth. So I let it warm up as long as possible to where it was at least 160*. And as I drove away I knew the ride to work was going to be interesting. The exhaust sounded drastically different... just like that top fuel dragster...

    Long story short(er), the engine was surging while in every gear and under 2500RPM... making that WHOMp WHOMp WHOMp kinda noise that I put in the subject line. If you read it outloud, thats actually just as quick as it makes the sound... It builds up power like normal (WHOM), and then basically dumps it (p) which sounds a lot like a back fire almost but more subtle. WTF!

    Here's a quick run down on the engine & ign.:
    * Mallory Unilite distributor
    * Taylor 135* 8mm wires (for the 454)
    * Edelbrock 1910 carberator
    * 8* timing (measured three days ago)
    * no obvious sign of vacuumm leaks

    Can anyone out there take a stab at what is happening to my truck? Its nearly undrivable, and makes almost no power which is dangerous in traffic where I live! /forums/images/graemlins/crazy.gif Any input welcome.

    Thanks all!

    -Dan
     
  2. Stoopalini

    Stoopalini 1/2 ton status

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    Re: My truck goes: \"WHOMp WHOMp WHOMp..\" help!

    Sounds like it's either running very rich (any smoke out of the pipes?), or you have a bad misfire (any arcing under the hood? broken plugs?).

    My truck sounds like what you are describing when my Holley acts up on me, which is about once a week /forums/images/graemlins/mad.gif (I hate that Holley!). It runs real rich and puffs some smoke at idle.

    Good luck,
    Thomas.
     
  3. KRAZIE87K5

    KRAZIE87K5 1/2 ton status

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    Re: My truck goes: \"WHOMp WHOMp WHOMp..\" help!

    Well... it does slightly smoke out the pipes, but the exhaust certainly smells SUPER rich. Another thing I noticed when doing the timing was that the timing light was not consisently blinking... IE maybe I have an intermittant spark? Plugs I can replace for very little $, so I'll do that regardless... WIRES cost $60 for my application... so I think I will test all of them before I go replacing them. Any other reasons you can see the spark appearing to be inconsistant through the timing light? /forums/images/graemlins/confused.gif

    -Dan
     
  4. Bullet

    Bullet 1/2 ton status

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    Re: My truck goes: \"WHOMp WHOMp WHOMp..\" help!

    What about a broken valve spring? I happened to me and it made the Jimmy idle like a top fuel dragster and made it almost impossible to to drive. I doubt that could be the problem but thought I might add my .02 /forums/images/graemlins/thumb.gif
     
  5. KRAZIE87K5

    KRAZIE87K5 1/2 ton status

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    Re: My truck goes: \"WHOMp WHOMp WHOMp..\" help!

    Damn... now THAT would suck. /forums/images/graemlins/frown.gif Guess I'll be pulling the valve covers too then... but wouldn't I hear something in the engine? I've literally sat under the hood listening for anything odd... and I hear nothing but a normal engine. BTW - the top fuel dragster sounds chill out somewhat once the engine is at temp, and the choke is open. So once the idle smoothes out, the engine sounds fine, with no obvious strange noises... :-p This sux. /forums/images/graemlins/frown.gif

    -Dan
     
  6. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Re: My truck goes: \"WHOMp WHOMp WHOMp..\" help!

    Check the obvious first...inoperative choke. If the choke won't open it'll do exactly what you described.

    Rene
     
  7. KRAZIE87K5

    KRAZIE87K5 1/2 ton status

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    Re: My truck goes: \"WHOMp WHOMp WHOMp..\" help!

    Okay... can you gimme the quick "down and dirty" version of how to adjust the choke correctly Rene? I know I can buy this book or whatever... but I don't want to spend the money as I plan to ditch the carb ASAP in favor of fuel injection. Maybe you have a link to a page that will tell me what to do? Thanks.

    -Dan
     
  8. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Re: My truck goes: \"WHOMp WHOMp WHOMp..\" help!

    Check that the choke is getting 12 Volts first. Loosen the three screws holding the choke housing and with the engine dead cold and primed (blip the throttle to 'set' the choke) the choke butterfly should be almost completely closed. Rotate the choke housing til it opens the choke butterfly and then rotate it back until the choke butterfly is about 1/8" from completely closed and tighten the screws. There should be some scribe marks on the choke housing...generally the middle marks work well.

    Now fire it up and watch the choke do it's thing. It should begin to open within 30 seconds or so and steadily open over a few minutes. Unless it's really cold the choke butterfly should be completely open within 5 minutes.

    Rene
     
  9. imiceman44

    imiceman44 1 ton status

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    Re: My truck goes: \"WHOMp WHOMp WHOMp..\" help!

    Do a compression check. it will show a problem in valves.
    Also check for exhaust leaks, that is what I had and it really drove like a dog.
     
  10. milspecjimmy

    milspecjimmy 1/2 ton status

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    Re: My truck goes: \"WHOMp WHOMp WHOMp..\" help!

    do you have headders? i had a set of hoker long tubes on my 89 jimmy, and it would do exactly as you described. surge then drop all in rapid succesion, and the ses light would some on. if i shut it off and turn it back on it would come out of it for a second. the problem i had was that when i was idleing, the headders would cool off letting the O2 sensor cool off. and it would trip the ecu into thinking it was lean and end up dumping the fuel into it making it surge. in my case the 02 sensor was at the collector. if you have headders check this out. you can either re-locate the sensor closed to the head. or get a heated 02 sensor.
    good luck
    /forums/images/graemlins/usaflag.gif /forums/images/graemlins/k5.gif /forums/images/graemlins/usaflag.gif
     
  11. KRAZIE87K5

    KRAZIE87K5 1/2 ton status

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    Re: My truck goes: \"WHOMp WHOMp WHOMp..\" help!

    Damn... if I was injected, I would hope this wouldn't be a problem at all! /forums/images/graemlins/wink.gif Heated O2 has already been discussed and added to the cost of my **hopefully** soon to be purchased EFI kit. /forums/images/graemlins/cool.gif I think the moral of the story here is a rich mixture.

    Can it be so rich, that the plugs foul? What would cause that in my carb? Keep in mind, its the Edelbrock 1910 850cfm offroad carb...

    Thanks again all....
    -Dan
     
  12. TopOff

    TopOff 1/2 ton status

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    Re: My truck goes: \"WHOMp WHOMp WHOMp..\" help!

    AHh the infamous dirty Edelbrock carbuerator problem. I am surprised you haven't had this problem before.

    Are you using those glass fuel filters? The kind that you can see the filter and all the crap in the gas?

    Anyway, my Edelbrock (electric choke) did this when the jets got dirty. Edelbrock's own manual specifies the gas needs to be VERY clean or irradic behavior will result.

    I ended up blowing it out, still had the problem, I thought the problem was elsewhere. Then I used a small wire and cleaned the jets, put it back on an voila' all was well. I ended using some fuel-injection type filters. These do some great filtering, yet plug up fast in my 3 year old 31 gallon rusting tank.

    My Edelbrock would barely let my 383 idle. It made it sound like it would almost backfire through the carb yet didn't I wouldn't get any power until ~2500 and sometimes it idled at 2000-3000 rpms!

    That was scary trip as I was towing the boat!

    It could also be a loos plug wire or two.

    Good luck.
     
  13. KRAZIE87K5

    KRAZIE87K5 1/2 ton status

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    Re: My truck goes: \"WHOMp WHOMp WHOMp..\" help!

    AH HA! I like this option best. And your description of how yours acted sounds JUST LIKE what mine is doing! Now I just need to figure my way around getting the jets out to clean them! /forums/images/graemlins/tongue.gif Pointers?

    -Dan
     
  14. KRAZIE87K5

    KRAZIE87K5 1/2 ton status

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    Re: My truck goes: \"WHOMp WHOMp WHOMp..\" help!

    Thanks Rene! I'll do that tonight in addition to cleaning the Jets off... /forums/images/graemlins/wink.gif /forums/images/graemlins/cool.gif /forums/images/graemlins/smile.gif Glad I have some good ideas to start with now...

    -Dan
     
  15. TopOff

    TopOff 1/2 ton status

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    Re: My truck goes: \"WHOMp WHOMp WHOMp..\" help!

    Just take the carb off. Take the top part of the carb off, and see if there are any small bits of rust and what not in there. If there are, I would guess this is indeed your problem. Clean all of the ugly little bits out and blow some air (100PSI or so) from the bottom of the jets. Clean it all up and put it back on and see if it works.

    If not, find a small wire that will go into the jets and clean 'em. Try it again.

    Good luck.
     
  16. HarryH3

    HarryH3 1 ton status Author

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    Re: My truck goes: \"WHOMp WHOMp WHOMp..\" help!

    Dan, I'm beginning to think that you need to hire an exorcist for that truck! /forums/images/graemlins/shocked.gif It seems to have a lot of odd problems! /forums/images/graemlins/wink.gif
     
  17. KRAZIE87K5

    KRAZIE87K5 1/2 ton status

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    Re: My truck goes: \"WHOMp WHOMp WHOMp..\" help!

    Shoot! Sign me up for two!!!! /forums/images/graemlins/laugh.gif

    -Dan
     
  18. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Re: My truck goes: \"WHOMp WHOMp WHOMp..\" help!

    Tip cleaners for a Oxy/Acetylene torch would work for the jets...many choices of very small wire!

    Rene
     
  19. thatK30guy

    thatK30guy 1 ton status Premium Member

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    Re: My truck goes: \"WHOMp WHOMp WHOMp..\" help!

    Kind of sounds like how my 454 was running for some time like this. /forums/images/graemlins/tongue.gif

    I hate to tell you, but this is what my motor's problem was that seemed to run like yours.......bent pushrod/s and/or bad lifters. /forums/images/graemlins/frown.gif /forums/images/graemlins/tongue.gif

    Don't take my word for it, but I'm just gonna say check those as a "last resort", when nothing else the others have suggested you to do, and nothing else is the cure for it...check out what I just quoted above. /forums/images/graemlins/frown.gif
     
  20. KRAZIE87K5

    KRAZIE87K5 1/2 ton status

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    Re: My truck goes: \"WHOMp WHOMp WHOMp..\" help!

    WESTY! Damnit... stop being the voice of the devil! /forums/images/graemlins/angryfire.gif /forums/images/graemlins/grin.gif I've already done the bent pushrods/bad lift thing, and it was NOTHING like this. The surging is SO bad that I can feel the suspension almost completely cycle! The figgin thing really lurches. That and the exhaust smells like fuel... and lots of it. I'm going to hope that its the carb! /forums/images/graemlins/ignore.gif So stop with your ideas of trashing my top end of my motor *again*! /forums/images/graemlins/1zhelp.gif /forums/images/graemlins/rolleyes.gif But thanks anywho for the idea... like you said, if all else fails, I'll check your idea at that point!

    -Dan
     

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