Post 120K Engine Failure

Discussion in 'Gen 1 & 2 - Engine, Exhaust, Drive Line & AC syste' started by myotis1134, Jun 19, 2020.

  1. myotis1134

    myotis1134 SHO Member

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    Hey guys, here's the situation:

    After redoing ALL of the coolant line hose clamps yesterday (long story), I buttoned up the intake manifold and was finally "done" with the 120K. It held coolant this time, and no oil was leaking from being filled 3 days ago. I hooked up the battery, primed the rail a few times, and turned the key. The engine sputtered and coughed for about 5 seconds then fired up and stayed running. The ragged idle left lots to be desired, but I couldn't have screwed up TOO bad if the damn thing was running...

    Then after about 30 seconds it began to surge - the idle steadily climbed,hovered then steadily dropped (about the same RPM) downwards. It would surge back up a little higher than before, then drop a little lower than before, and I could see where it was leading so I shut it down. Probably less than a minute running before I killed it.

    I walked over to the house and started searching the forums to see if anyone had run into this before, and found a thread about the IAC valve, and how it can cause surging. So I went back to the shop to take a look and found that I had not hooked up this connector.

    IMG_1924.jpg

    After plugging in the connector I attempted to start the vehicle, but it will not fire. I can smell gas a little when I crank it a lot so the fuel side of things seems to be working. I was quasi-OCD with making sure the various electrical connectors were clean and dielectric-greased up, and I didn't see any tweaked connector blades while cleaning them out. I was also very anal about making my grounds clean, and have added several besides what's stock.

    I am currently in the process of re-installing the IAC valve. I have inspected it and found it to be in good condition as far as I can tell. It was fairly clean inside, and all the gaskets were especially hardy and difficult to remove. I sprayed out the valve portion of the IAC with carb-cleaner, and I have electrical cleaner for the magnet portion.

    IMG_1920.jpg

    Looking into the throttle body, it appears to be a little grimy/oily, and if I can find a gasket locally I will remove the TB and clean the hell out of it. The airbox side is clean, and doesn't look too bad behind the butterfly.

    The MAF looked clean before I started the 120K, but I got spray for it and will hit it tomorrow - just in case.

    Where do I go from here? Is it possible that I fucked up the timing when I replaced the belt? Should I be looking into whether or not my spark plugs are firing?

    I'd appreciate it if someone would point me in a direction on this. Thanks in advance

    p.s. Do these tires work?

    IMG_1926.JPG
     
  2. rubydist

    rubydist SHO Master Staff Member Super Moderators

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    The most likely thing is that the timing belt is not on correctly. You can double check that by only taking off the upper timing belt cover, turning over the engine until the crank pulley is at the correct orientation and then checking to see that the timing sprockets align with the marks on the metal part of the top timing cover. (Remember that the crank turns 2 revs for each rev of the cams, so you may have to turn the engine over one additional revolution to get the cams in the proper orientation.)
     
  3. zoomlater

    zoomlater SHO Member Supporting Member

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    Did the car run fine previously with your current IAC valve? If so, then it is probably still good.

    Are those new silicone hoses between the butterflys and intake? Those look like some pretty heavy duty hose clamps. I noticed you only have one centered on each silicone hose. Typically there are two hose clamps, one on either ends of the hose so it seals against the butterfly and intake. I am wondering if you have a vacuum leaks since you are compressing the center of the hose. It depends if the edge of the clamps are overlapping the intake and butterfly ends.
     
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  4. luigisho

    luigisho SHO Member

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    I am also curious about how it ran before the 120k. Also did you loosen the clamps on the intake before you put it back on? I can seat a little off if there is no flex. So a little flex to get the intake bottom to seat flush on each side and then retighten.
     
  5. myotis1134

    myotis1134 SHO Member

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    @zoomlater - the car ran very well up to the point where one of the spark plug well gaskets leaked and fried/fouled a plug. Even then it ran fairly well, except for when I put my foot in it.

    I cut all those couplings out of some hardcore silicone hose back in the day. The walls are pretty thick and rigid, and when I first put them on the intake, I very nearly didn't use any clamps because the were so tight. Not so much these days, and I'm going to swap them out with a shosource kit.

    @luigisho - It ran fairly ok. I could hear that a spark plug was dead.

    I followed the SHO Phoenix Project 120K manual for this - as closely as I could, excepting for where torque specifications weren't mentioned and I had to do research.

    I did loosen all the coupling-hose-clamps for intake manifold installation... twice - after the first installation I discovered a few of the fancy, awesome-looking, expensive hose clamps I upgraded with were allowing coolant to leak all over the engine and floor. Couldn't trust the rest of them after that, since the leakers were sized and installed correctly.

    @rubydist - That's what I was afraid of. Shit.
     
  6. sperold

    sperold Last to Know Supporting Member

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    Have a look at the codes, active and stored. The IAC will generate a code. Sometimes a TPS will act up, but again, the codes will tell you.

    You should be able to coax it back to starting like it did at first, before you do any belt work.
    Make sure your fuel pump does the little buzz, try some quick start in the intake tubing, and use an extra spark plug to see if it is firing. Make sure your 10A fuse that supplies the coils and the coolant level sensor is OK.

    Usually it is the last thing you touched that is the problem; but sometimes it is just a coincidence that another issue shows up and muddies the waters.

    Again, read the codes first.
     
    Last edited: Jun 19, 2020
  7. myotis1134

    myotis1134 SHO Member

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    Hat is off to rubydist - I've gotten down to the timing belt, and I have no idea how it got this out of whack...

    IMG_1931.jpg

    And on bottom:

    IMG_1929 - Copy.jpg

    It's embarrassing. No idea how that happened. Follow up to follow.
     
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  8. rubydist

    rubydist SHO Master Staff Member Super Moderators

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    In my experience, that is the most common problem when changing the timing belt - when you go to slip it on the sprockets, the "tight" side of the belt has some slack on it, so when its tensioned the belt is 1 or sometimes 2 teeth off. The trick is to have the crank turned 1 tooth farther counterclockwise when you are installing the belt, so that when you tension the belt the crank is in the right spot. The engine will run that way, but poorly as you have discovered.
     
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  9. myotis1134

    myotis1134 SHO Member

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    So I've realigned everything, but run into an issue - when putting tension on the belt, the rear cam sprocket rotates counterclockwise slightly. Front sprocket and crank stay aligned. Is this acceptable, or am I putting too much tension on the belt?

    IMG_1936.jpg
     
  10. luigisho

    luigisho SHO Member

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    Am I right in recalling there was a cam tool to keep the sprockets from moving? Not that it was used much but maybe a little home made something to keep them still.
     
  11. myotis1134

    myotis1134 SHO Member

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    So the timing marks all need to be dead nuts? If that's the case, then it appears that I'll need to reduce the amount of tension I apply to the belt.

    I've been looking for something definitive on how to properly configure the tensioner, and between the shophoenix walk-through, and this 1989 STST SHO engine manual, I still have no idea if I'm doing this correctly. The tensioner isn't that complicated, but is it my call on how tight i make it, or should it be rotated to place maximum potential tension against the belt?

    If Maximum tension is required, I'll need to figure out how to prevent the rear crank sprocket from backing away from its timing mark, but after the tensioner is locked down - won't the sprocket back off anyways when equilibrium asserts itself?
     
  12. myotis1134

    myotis1134 SHO Member

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    Think I've got a handle on this. Apparently I was stopping the rotation of the tensioner too soon, so it was not able to give with the belt movement.

    What are the odds that I've managed to screw up this timing belt?
     
  13. luigisho

    luigisho SHO Member

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    let's be hopeful and say 30/70
    fire it up!
     
  14. rubydist

    rubydist SHO Master Staff Member Super Moderators

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    dont worry about it, just carry on. you should be fine now.
     
  15. rubydist

    rubydist SHO Master Staff Member Super Moderators

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    but, make sure there is not too much tension on the belt - I have seen a cam fail due to too much load from belt tension.
     
  16. FastCAD

    FastCAD SHO Member

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    If you still have the IAC installed dis-connect the wiring "then start the car" (you might need to to feather the gas pedal to keep it running if it is cold). When it is warm let it idle. Let the car re-learn "base" idle (about 800 rpm) then plug in the wiring.

    Don't forget that a dis-connected battery will erase the ECU memory and will need to re-learn. So the SHO will run somewhat badly until you put about ten miles on the clock.

    If the rpm's still surges up and down then the IAC is bad or (just dirty). It can be cleaned. Either way it is a pita to replace. Do yourself a favor if you decide to replace the IAC. Be sure to get the correct one and a quality unit. Delphi (fuel injected) is same as the OEM unit. If you cheap out on an inferior product then you will do the job twice.

    Note: The throttle position sensor will give similar surge conditions but the sensor will throw a code the IAC does not.

    Best to ya.
     
  17. myotis1134

    myotis1134 SHO Member

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    Picked up a new DIS from shosource, and a new IAC valve locally.
    Can’t do much for another day or two while I wait for a new water pump neck gasket - which I discovered had a small leak - while I was screwing around with the timing.

    I’m staying busy with the intake - currently scrubbing components in a bucket of simple green, with a toothbrush... yes I need a life. But I found that I had done something to the intake manifold the last time I did a 60K, and it strikes me as odd now.
    Apparently I used some sort of rtv gasket maker on all the mating surfaces, plus the gaskets. This has made the act of removing those gaskets a real bitch, and I’m really not sure if I was just being anal retentive, or really believed it was necessary to ensure that level of integrity.

    CA7F3485-8057-4208-BC4F-93FF0B9A93AA.jpeg

    Anyone ever felt the need to go beyond standard gaskets on their intake manifolds?
     
  18. luigisho

    luigisho SHO Member

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    Actually, no. That's one of the few places I didn't worry as much. As long as everything is flush and the regular gaskets are good.
     
  19. myotis1134

    myotis1134 SHO Member

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    In the process of replacing all the fasteners on the intake manifold assembly. The valve screws were problematic initially, because I asked a ‘professional’ to identify the thread and pitch.
    After he informed me that he had never seen that particular bolt/screw thread before, I took it to the home depot and found it to be an M3-0.5 x 5mm bolt (I guess it’s technically a bolt).
    I really wanted something on there that doesn’t require a regular driver head for removal, and I would recommend a button-head torx - since that will keep you fairly aerodynamic but still make that head a little beefier.
    Unfortunately for me, between every fastener shop in town, I was only able to come up with socket-caps - they look cool, but poke out pretty damn far into the volume.
    I’m curious if anyone has any experience with this sort of scenario, since I’m getting ready to button everything back up, and would rather fix any potential problems while it’s convenient to do so.

    DF91E775-5658-40AA-BE0A-6E5484487F3A.jpeg

    image.jpg
     
  20. luigisho

    luigisho SHO Member

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    I haven't seen one of those apart in ages. Maybe try a deep search. I remember posts from a long time ago about doing this and some pics but those might be lost to a server crash along the way. There should be an owner or two around that did this or switched to BBB that had to do this. Maybe Toolman not sure if Chad did this. Who else is still around from the way way back? Jayson that does tuning for the blue turd. Maybe past and present shosource guys?
     
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