1uzfe knocking

Discussion in 'Diagnostic & Repair Tech' started by fabre12, Nov 22, 2018.

  1. fabre12

    fabre12 New Member

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    Hi fellow 1uzfe owners, apologies for the long winded post, but this quite a story.
    We are in the middle of a transplant of a 92 1uz from a SC400, we have recently had issues with the beast not idling when cold. After research, we concluded that the ECU caps my be the problem. We took the ECU to a family member who is an electronic engineer and repairs all sorts of devices(but has never done an ECU). We bought all the capacitors from digikey.com after lots of research. The said family member had lots of trouble replacing the capacitors, and 1 was not changed due to access. A few were very tricky and he was not confident, but we pushed on as he did the worst looking capacitors. Before we installed the ECU again, we replaced the spark plug leads, rotor buttons, and dizzy caps, and re-sealed the rocker cover gaskets. After putting everything back together and starting the beast, it was clear that the ECU was not right, it still would not idle, and was running very roughly. All of a sudden the engine stopped for no reason, and would not turn with the starter motor. we removed all the spark plugs and then turned the motor with the starter, then one of the cylinders shot out a stream of fuel across the garage. We concluded that the injector for that cylinder was stuck open and the motor was hydralocked with fuel. We turned it with the starter motor for a few minutes to get all the fuel out. Next we got another ECU and plugged it in and it seemed to idle okay, but we noticed a knocking noise which seemed to happen every turn of the LH camshaft.
    We have taken nearly all of the front of the engine off looking for something to cause the knocking as it seemed to sound external. The only thing left on the front is the timing belt and idlers and tensioner. Today we checked the compression on all cylinders, and they are all over 175psi. This is driving us nuts!
    The other noteworthy clue is that if we turn the motor by had on the front crank pulley bolt, it locks when the same cylinder that hydralocked is at Top Dead Centre. If we force it, it will go past this point, but will always lock at the same point. We don't really want to tear the motor apart looking for the issue unless we really have to.
    Any clues would be welcome as we are stuck for ideas.
    Thanks in advance.
    By the way, we are running this engine in a 2000 Jeep Wrangler with plans of taking the beast off road eventually, as well as taking the caravan away every now and then.
     
  2. American Locomotive

    American Locomotive New Member

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    Hey, we also have a 1UZ in a Wrangler!

    Unfortunately your engine is likely toast if it hydro locked that hard. The connecting rod for that cylinder is likely bent, or the valves for that cylinder are likely in distress from trying to open to a cylinder full of fluid. I'd start by checking the valve clearance. If it checks out, you are going to have to pull the cylinder head and oil pan and replace that piston and rod.
     
  3. gloverman

    gloverman Well-Known Member

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    Im kind of thinking out loud.

    If its bent a rod then it might be possible to measure it through the spark plug hole.

    Being a generation 1 engine its a non interference unit however ive had a few which have had carbon fall between the head and piston. This is mainly after they have been sitting however a soaking of fuel might do it too.

    Im thinking the above post suggesting valve train issue is a good one too. Ive had one spit out a adjusting shim and another split a bucket.

    Again being non interferance you could turn it over with cambelt fitted to see if it sticks without the cams turning and turn cams over with belt off to see if its top end.

    And at the end of the day these engines flick apart pretty easy if it the issue is worse case scenario.
     
  4. ivan129

    ivan129 1UZ300ZX

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    Hi fabre12, Your description doesn't seem to make sense to me. If I'm reading this correctly you claim that the cylinder that locked up because of being full of fuel made 175PSI comp, the same as the other cylinders? If that's the case you can't have a valve problem or piston ring / seal problem. I had a engine that developed a stuck exhaust valve (fully open) and it just had a miss. This was easy to pick up with a comp test. I would pull the plugs and see if you can identify where in the cycle the engine has the sticking spot. Hone in on the suspect cylinder.. Is it at the top of the stroke? If its at the bottom you could have broken a piston... maybe
     
  5. fabre12

    fabre12 New Member

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    Hi Ivan, it locks when number 5 piston(the one that hydra-locked) is at TDC
    We have since removed the cam belt to see if it makes a difference, and there is no difference, it locks at the place every 360 degrees!
    We tried turning the cams manually to see if it changed when it locked, but no change, starting to look like a rod or piston problem, but it has good compression!
     
  6. fabre12

    fabre12 New Member

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    Hi Loco, what Wrangler do you have? Ours is a TJ. What trans/transfer are you running?
    Would it still have good compression if there were any issues with valves or piston or rod?
     
  7. fabre12

    fabre12 New Member

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    Just spoke to a workshop nearby, they seem to be sure that the big end bearing shell has been crushed and the con rod is "floating" and causing it to hit the block.
    Anyone heard of big end bearings failing?
     
  8. ivan129

    ivan129 1UZ300ZX

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    I very much doubt that its the big end and given your stating its at TDC for No. 5, the crank will have the BE at the top of the rotation so nothing for it to hit. Its gotta be related to something in the No.5 combustion chamber. Have you lifted the cams and buckets to confirm the tops of the valves are at their correct height. It sound like the collects have come off a valve and allowed a valve to drop down into the chamber. The valve seal and stem seal would probably stop it from falling all the way into the cylinder. The big problem with this theory though is you sure as hell wouldn't have 175PSI comp if what I've just proposed is the problem. I recon your gonna have to lift that head and take a look inside.
     
  9. ivan129

    ivan129 1UZ300ZX

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    I recon you have broken No. 5 piston possibly around the ring lands. This theory matches all the symptoms described. The top of the piston has cantered side ways just enough to fowl with the combustion chamber but not enough to stop it from making compression. Let me know if I win the cigar. Regards Ivan
     
  10. fabre12

    fabre12 New Member

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    Does anyone think having this much variation between cylinders is okay?
    I know I'm pulling at straws, but this is driving me nuts, I don't really want to start pulling it apart, but the longer this goes on, the more likely that's what I'll have to do.
     

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  11. ivan129

    ivan129 1UZ300ZX

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    Dude, get the head off that sucker and take a look, or don't you know how to? Did you lift the cams, shims and buckets to take a look at the tops of the valves like I suggested above? Let me answer this question for you... No. Your gonna waste more time asking others and wondering instead of getting on with the job. Its less than an hours work... but I'm guessing it will only show that your got to pull the engine anyway if its a busted piston. You might be lucky if its head. Bite the bullet and get on with it!
     
  12. Zuffen

    Zuffen Super Moderator Staff Member

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    +1 for Ivan.

    With that much variation in compression you're never going to fix it from outside the engine.

    Grab your tools and get down and dirty.

    Head off to have a look and probably just buy a replacement engine as its cheaper than a gasket set.
     
  13. fabre12

    fabre12 New Member

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    Looks like you're not getting the cigar, even if you end up being right!
    What's with the attitude DUDE?
    Some people have other things to do with their lives and can only work on their hobbies every now and then!
    If you don't like anything I'm asking or typing, it's pretty simple DUDE, stop looking!

    Meanwhile others will continue to be helpful and offer constructive advice and we might all learn something.
     
  14. fabre12

    fabre12 New Member

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    Yes, we are thinking the same thing, we are already pricing another engine.
    It will still be worth tearing it down just to learn what these look like inside.
     
  15. Zuffen

    Zuffen Super Moderator Staff Member

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    Please let us know what you find.

    I would have thought after hydro-locking that the likely-hood of a bent rod was quite high.

    A shattered piston would give no compression but your figures do show a large discrepancy.
     
  16. ivan129

    ivan129 1UZ300ZX

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    Dude if you take offence from that then its clear you have more time to stew over your computer than for your project. What I offered you was some help but its clear you can't see that. The problem has been diagnosed for you. Get the spanners out and get on with the job. You got time to sit at your PC, spend that time on the project.
     
  17. Zuffen

    Zuffen Super Moderator Staff Member

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    Neutral corners please gents.
     
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  18. fabre12

    fabre12 New Member

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    I think we found the problem@
     

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  19. fabre12

    fabre12 New Member

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    It was number 3 piston scrapping against the counterweight.
     
  20. Zuffen

    Zuffen Super Moderator Staff Member

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    For that to happen the rod would need to be bent to shorten the distance between the counterweight and the piston?
     

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