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1990 1500

Discussion in 'GM Powertrain' started by steps350, Jan 5, 2011.

  1. steps350

    steps350 New Member

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    Hey all Just wanted to say Hi , Iam new here my name is Corey, and i live in lethbridge alberta. I just bought a 1990 gmc 1500 4x4 for $750. it runs and drives . Iam just wondering the exhuast is cut off right after the cats and upon cold starts there seems to be a ticking noise coming from the exhuast , once it warms up the ticking gets quieter, I lisened in the engine bay and by the exhuast and iam pretty sure its coming from the exhuast, could cutting it off right after the cats make this noise?
    thanks all in advance
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  2. dualdj1

    dualdj1 New Member

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    could just be lifters ticking. Have you changed oil since you got it? might want to run some system treatment/cleaner though it.
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  3. steps350

    steps350 New Member

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    ya I just did a whole tune up last night iam goin to check the timming today there seems to be a miss at idle
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  4. ejohnson03

    ejohnson03 New Member

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    If the Header or Collector gaskets are lstarting to leak, you will also hear some ticking.

    Gaskets are cheap, just replace them and rule out that as an issue.
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  5. silveradotrailblazer

    silveradotrailblazer New Member

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    Welcome to the club, Corey.
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  6. stephan

    stephan New Member

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    Hey Cory, welcome to the club. X2 on EJs exhaust gaskets repl. since you're hearing the ticking noise at the exhaust
    #6
  7. steps350

    steps350 New Member

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    hey guys thanks for the info and I love the site, yea long story short I bought the truck off of a farmer that I dont think has ever done any tune ups on the truck, the plugs where beyond fouled same at the dis cap and rotor so iam in the middle of trrying to get it all tuned up, it just seems low on power like when its idling and when you step on it , it seems dosnt seem to be hitting on all the cylinders i have timed it , any suggestions?
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  8. stephan

    stephan New Member

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    Since you don't know any of the maintenance history on this rig, I would warm the engine up to operating temp, pull the plugs & do a compression check. Even better would be to do a leak down test if you know somebody you could borrow the guages from. You mentioned fouled plugs. Were they wet fouled? If so, with oil or gas? Your miss could be plug wires if you haven't replaced them yet, but you need to find out if the rings & valves are sound on all 8 cyls. first.
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  9. steps350

    steps350 New Member

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    yea on # 8 cylinder I pulled the new plug and it was a little wet with what looked like a little oil so thats kinda got me worried, the engine only has about 160xxx kms on it but thats all I got left is to do the wires
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  10. stephan

    stephan New Member

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    ok, a little oil on one plug isn't so bad. You might try putting a 1 step hotter plug in that cyl to keep it burned off, but I would definitely do at least a compression check. Since you got it from a farmer, he might have started it 10-20 times a day to stock feed etc & it may have never gotten warmed up or ever seen the roads. He might have used it exclusively in the fields.
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  11. steps350

    steps350 New Member

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    ok i will do a compression check when I get home tomorow night and post up the resualts, thanks again for all the help
    #11
  12. steps350

    steps350 New Member

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    hey I just ran a compression test and all the cylinders were between 145-147 the number 8 cylinder was 30 any sugestions
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  13. stephan

    stephan New Member

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    That's bad news. The easiest thing to do first, is take off the valve cover & see if you have a weak or broken valve spring. If you're lucky this will be what it is cuz you can replace one or both fairly easy, (without taking the head off) but I'm afraid you won't be so lucky. I think you have either a burnt valve, broken rings, a bad head gasket, a cracked head, or a cracked piston. Which ever it is, you're going to have to pull the head off & have a look. No need to waste time diagnosing it any further cuz this one is going to be obvious. 30 psi is nothing. Gas needs a minimum of 90-100psi to fire correctly & contribute to anything near a smooth running engine.
    #13
  14. steps350

    steps350 New Member

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    hey I had the valve cover off while it was running , both rockers seemed to be moving same as all the other rockers , how else do you tell if the springs are bad
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  15. stephan

    stephan New Member

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    The rockers will be moving the same because they are controlled by the cam, lifters, & push rods.
    Did you hear one of the #8 springs clicking or clattering more than the other 6 on that side?
    If not then the best way to check is to turn the engine over by hand untill both #8 valves are closed (springs all the way up & relaxed) Take a piece of wood & push on the spring end of both rockers. Is one easier to push down than the other? Try comparing them to a couple of other springs on that side that are also relaxed (valves closed position) If you don't notice any difference then the springs are not weak or broken. (You can also do a visual on the springs for breakage)
    If this isn't a spring problem, then it's definitely inside & you're going to have to pull the head off.
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  16. steps350

    steps350 New Member

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    ok I will try the springs in the morning and post up resualts hey do you think the valves could just be gummed up or stuck because the oil was really old the top of the valve covers were caked with old oil
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  17. stephan

    stephan New Member

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    They'd have to be stuck to the point that one of them wasn't closing in order to be losing 115psi out through the seat. Also if it was gummy valve stems or guides, I would be expecting to see the same issues with one or two of the other cylinders, but they are ALL even at 145-147. I'm still hopeing this is a broken spring, cuz it is the easiest & cheapest fix. Even if they both pass this test tomorrow, before you pull the head off, pull the 2 rockers off #8 & grab these 2 springs & rotate them around so you can see all sides of every coil. If your retainers are the "umbrella type" the top 3/8" of the spring could be broken & would be difficult to see. Also press down on the springs again without the rockers on there & see if one is weak. If this is a spring issue, you want to find it before you pull the head off.

    ** One other thing you can do is check the height of the springs/valve stems. Lay a straight edge across the tops & see if one is lower than the other. Something could have circulated through the engine & gotten stuck between the valve & the seat (doubtful, but it's possible)
    Last edited: Jan 6, 2011
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  18. steps350

    steps350 New Member

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    ok i will do that in the morning and then post resaults , thanks again
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  19. dualdj1

    dualdj1 New Member

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    Stephan's right on in checking the springs first. However with it having oil on the plug, unless the stem seal is bad (also possible), i'm thinking your problem is in the bottom end, unfortunately.

    Now, depending on what you're going to do with it, you can probably run it this way for a while. likely the farmer you got it from has been doing so. So if you don't have the time/money currently to pull the engine down, you can probably get by as is for a while. But still would at some point want to pull the engine and rebuild, or put in another used/rebuilt engine.
    Last edited: Jan 7, 2011
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  20. steps350

    steps350 New Member

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    yea that was what I was scared of, i am goin to go check the springs in just a little bit today also i will try and squirt a little oil down the cylinder to see if the compressio jumps up any, but i was goin to ask ive been looking around and I found a 1998 vorteck 5.7 , if I put my old manifold on it with my tbi would it bolt right in?
    #20

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