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Help identify terrible noise

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by 86blazerk5, May 26, 2002.

  1. 86blazerk5

    86blazerk5 1/2 ton status

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    Hey guys, I have posted about this before becuase i thought it was part of my exhaust system. I had a factory cat with holes in it and my pipe was riding on the frame. I thought that when i reached a certain rpm that that cuased it to rattle against the fram rail... However, I have had that section of my exhasut redone. I have a brand new cat, and a new pipe that dosnt sit on the frame. Not only is the noise still there it is getting louder and doing it more often. I also thought it could be a heat sehild at one point point. But it is to loud foir that and my cat heat sheild is tight. It only does when I am on the gas in such a way minimaly, or averagely. If I am on the gas hard, it dosnt do it. Also, it really only does it up hills under load. It sounds like a super loud vavle tapping. Its verry fast and hard sounding like that, but it is a lot louder. I am pretty sure it is coming from the Transmission now. But would like more opinions before i take it to the tranny shop. The trannys under warrenty so its no big deal. But I just want to be sure thats what it is. I cant stand it much longer. Please help. I am no expert, But I feel like it may have to do with the Torque converter or somethi g in there. Its a 700R4.
    Thanks.
    Ike
     
  2. UseYourBlinker

    UseYourBlinker 1 ton status

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    Are you still running an EFE valve on the passenger side? It's sandwiched between the manifold,and the collector pipe. Mine broke the welds and made a horrible noise. It would get louder when I would push the gas more.
     
  3. 86blazerk5

    86blazerk5 1/2 ton status

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    yes, i am still running one. I will have to check that, but I dont think thats what it is becuase it goes away when I push the gas real hard. Its just when i am on the gas maderatly under load up a hill...
    Ike
     
  4. 86blazerk5

    86blazerk5 1/2 ton status

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    I just went out and looked at my EFE, it all looks good, and i am pretty sure it is coming from one specific side of the engine. However, as I was checking out the EFE, I noticed a verry damaged wire going to a plug in the engin in front of the starter motor. I looked it up in my haynes manual to find it is the ESC plug. It said that if this plug isnt getting current that the esc cannot advance and that can cause Spark Knock under load. Could this loud Noise be spark knock. I have to admit that i dont know what Spark Knock would sound like and i cant imagine it would be this loud. I mean this noise is loud. It sounds far louder than a diesel and it is an awful sound too... Just another bit of info for you guys to think about. Thanks.
    Ike
     
  5. jberg62

    jberg62 1/2 ton status

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    Yep, spark knock can get pretty loud.
    You very well of found the culprit of your phantom noise, but to be sure you're gonna have to repair the damaged wire and reconnect it before making that final determination.
    It shouldn't be too hard to fix, just run a new length of wire to the sensor; be sure to route it away from the exhaust system or any other areas which could burn the wire.
    God luck with it!
     
  6. 86blazerk5

    86blazerk5 1/2 ton status

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    Ok, well,if that is whta it is then I can try to fix it, but I need to know a few things. First of all, Do I need to get a particular gauge of wire. And second of all, Where does the wire go to. I am still not sure if this is the problem, but it is a good place to start. I am also curiouse if I have been driving it like this for a while now, could there be any extensive damage to my motor. Thanks for the help.
    Ike
     
  7. YtseJam

    YtseJam 1/2 ton status

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    Sounds like detonation to me. This can severly damage the engine. The first thing you should do is check the timing with a timing light. Once the timing is set if it still does it you probably have excessive carbon build up in the engine and or EGR passage. That can be helped by using Top Engine Cleaner. Top Engine Cleaner can be bought at any GM Dealer and works really good, but you need to change your oil after you use it or you will surely wipe out a bearing. As far as the wire in front of the starter, This should have a round connector on it going to the knock snsor in the engine block.
     
  8. jberg62

    jberg62 1/2 ton status

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    What gauge of wire to use would depend on what guage of wire the sensor is already using. What size wire is already there? I'll bet it's probably a 16 ga., the onlt reason I assumed that size wire is that it's a regularly used size in wiring harnesses but in order for you to be absolutely positive of what gauge wire it is you'll have to clip a small amount of it off and bring it someone who'd know what gauge it could be.
    I truly don't think that the gauge of the wire would make that much of a difference (if any) to the performance of the sensor in question.
    If anything a larger gauge wire is probably a better choice than the one that is currently being used, it wont hurt anything.
    The wire more than likely goes from the sensor back to the ECM (Engine Control Module) which would be located under the dash on the passenger side. It's a little black box which is about the size of an 8-track tape 4" x 6".
    You will never be sure if this is the problem until you mend the wiring that you see is messed up. Just use wire of the same diameter and a couple of solderless connectors and you should be all set.
    I think everything should revert back to normal once the sensor is repaired. I'm pretty sure that engine knock is due to the timing being mega off.
    I'm sorry for goin on and on here but I'm quite sure that you can fix this small wiring prob by yourself in no time.
    What color is the wire? Clean it off and find out.
    follow the wire for as far as you can and remove as much of the damaged area as possible...You can do it!!!
    YseJam said what to do next.
     
  9. 86blazerk5

    86blazerk5 1/2 ton status

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    Ok, well i am confident that i can change the wire. I am just not confident that that is going to solve the problem. Although i hope so. i really dont think it is the timing or detonation either, but it could be. I really kida think its coming from more below me than infront of me. Or the tranny or something. But Tomorrow i will change the wire. And see if that hopes. If not, hopefully my naighbor will be out in his garage. He's a mechanich who works out of his home garage. But I just hope he's out tomorrow, he may not be becuase of memorial day. But I want to solve this fast. If it is timing and detonation, he can find it and solve it. Or He can tell me its in the tranny and i can take it to my tranny shop. Out of curiostity. If it is Detoination. Would there be other signs besides The noise that only hapens under certain circumstaces. If so what are they...?
    thanks,
    Ike
     
  10. jberg62

    jberg62 1/2 ton status

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    No, that's about it. A sensor failure woul allow no spark retard, which means you'd be too far advanced whenstepping on it as you are (that sweet spot)
    The more I think about it and I'm no expert either by the way so please tell me what you do find out when you do find out what the problem is...'cause you will.
    It sounds as if you just recently got a lift installed and the driveshaft is binding under load (exceleration)
    I just went through that myself after installing a 6" lift system.
    The rear driveshaft cv joint was binding a bit, but only upon mild exceleration. I didn't notice it as much if I stepped into it real hard or not hard enough ya know.
    I ended up dropping the Transfer case down 2 1/8"!
    That's a bunch, usually t-cases only get dropped about 1 1/2"
    but I had to do what I had to do so I did it and what do ya know...the noise disappeared.
    So check out your driveshaft (where it enters your transfer case) for binding. It could be a worn u-joint in the rear driveshaft that's binding.
    Just another look at this problem. Another potential area for you to check into.
     
  11. 86blazerk5

    86blazerk5 1/2 ton status

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    well Guys, the update is this. I changed the electronic spak control wire. And i still have the problem. The more i play with it. The more sure i become that t is drivetrain Related. The engin is really running good. I am pleased with it.

    I didnt not recently install a lift. I installed my 4 inch lift 2 years ago, and i had the drive shaft lengthened. And the t-case lowered using the factory 1 and 1/2 inch spacers. There should be no binding. There may be however, a u-joint issue. Which I will check shortley. But i just replaced the u-joints 6 months ago or so. So I doubt its that. I am thinking that i could be haveing a t-case prob or a tranny prob and i say the becuase they were both recently rebuilt. but maybe somethign was put in wrong... I dont know what it could be, I just know thats where it sounds like its coming from. I know know if my tranny shops open today or not. Sometimes they do work holidays becuase they are busy. anymore sugestions anyone.
    Thanks,
    Ike
     
  12. 86blazerk5

    86blazerk5 1/2 ton status

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    Ok, well, I pulled the driveshaft and checked out the u-joints and they look pretty good. So, i dont thinks its them. But, i am pretty sure its in the drivetrain. So, tomorrow after work, I am going to stop by the tranny shop. So I guess well see what we find then.
    Ike
     
  13. Chris_T

    Chris_T 1/2 ton status

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    I've got a very similar vibration right now - also driveline related. Iy happened before and ended up being a loose T-case output yoke. It's doing it again now and the yoke is still tight, so I'm guessing T-case ouput bearing (of course it is, thats the only part of the driveline I haven't replaced yet). If you do find the culprit PM me as I'd love to hear what it is.
     
  14. 89Blazin

    89Blazin 1/2 ton status

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    How about checking your flex plate or flywheel/ TC area for cracks in plate etc.
     
  15. 1986Blazer

    1986Blazer 1/2 ton status

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    I've had torque converter bolts work themselves loose to the point they touch the flexplate and the tranny dust cover. It is a long shot but that is something that happened to me and it created an aweful noise.
     
  16. Blue85

    Blue85 Troll Premium Member

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    Check to make sure your rear pinion nut is tight. A loose pinion gear can make various death sounds based on the amount of torque in the drivetrain.
     
  17. 86blazerk5

    86blazerk5 1/2 ton status

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    Ok well, I went to the tranny shop and they rode with me and they seem to think it could be a cracked fluwheel that just flexes enough to hit the dust cover at just the right range. However, they wont know for sure until next tuesday. Thats the next time they could fit it in. However, it is definently coming from that area. I guess i'll have to fill you all in next week though . Thanks for the replys.
    Ike
     
  18. jberg62

    jberg62 1/2 ton status

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    Well then it looks as though 89Blazin nailed the diagnosis.
    Yes, plewase do tell us what is found to be the actual cause of the phantom noise; we'd be very interested to learn.
    Thanks!
     

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