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924RACR
Joined: 29 Jul 2001 Posts: 8816 Location: Royal Oak, MI, USA
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Posted: Thu Dec 01, 2016 10:49 pm Post subject: Pray for the '82 931... |
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Yes, mine... have been trying to get it back on the road after engine rebuild, but struggling. Was running, then injectors fouled out... replaced them, but still running badly and fouling plugs, lots of oil consumption and blowby... was thinking turbo, but now I'm thinking the rings (yes, on the NEW motor!!!) are fouled up and sticking, based on leakdown results - full leakage unless I move the cylinders, then we pick up some sealing, but still well down. (40-60% leakage).
Going to try to hit the cylinders with Marvel Mystery Oil, see if that clears things up - followed by an oil change of course. Cross fingers, say a prayer, and maybe sacrifice a chicken that this'll work and we'll have the Turbo back on the road again... though only to sit for the winter, and wait for good weather come spring... _________________ Vaughan Scott
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'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype |
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Fasteddie313
Joined: 29 Sep 2013 Posts: 2596 Location: MI
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Posted: Fri Dec 02, 2016 1:47 am Post subject: |
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What are the specs of your bores, pistons, and rings?
Did you bore the bores? If not, did you blueprint them? If so, did you blueprint them to check?
What pistons are you running? Are you POSITIVE of their size? Did you blueprint them?
Did you measure your ring gaps? _________________ 80 Turbo - Slightly Modified |
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Rasta Monsta
Joined: 12 Jul 2006 Posts: 11724 Location: PacNW
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Posted: Fri Dec 02, 2016 2:40 am Post subject: |
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Psst. . .Vaughan is an engineer
_________________ Toofah King Bad
- WeiBe (1987 924S 2.5t) - 931 S3
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924RACR
Joined: 29 Jul 2001 Posts: 8816 Location: Royal Oak, MI, USA
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Posted: Fri Dec 02, 2016 4:36 am Post subject: |
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Yeah. Bores were re-honed, original pistons.
Ran well for 500mi before put away for winter. Injectors developed clogging some time after starting driving again the following spring. Sat around most of the summer. _________________ Vaughan Scott
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'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
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924RACR
Joined: 29 Jul 2001 Posts: 8816 Location: Royal Oak, MI, USA
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Posted: Fri Dec 02, 2016 8:20 am Post subject: |
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Soaking in mysterious oil now... jiggled it back and forth a few... fingers crossed for improvement tomorrow... _________________ Vaughan Scott
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'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype |
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morghen
Joined: 21 Jan 2005 Posts: 8886 Location: Romania
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Posted: Fri Dec 02, 2016 5:42 pm Post subject: |
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how can you clog the injectors? i dont run my cars for 6 months or so and they start at quarter key every year. _________________ https://www.the924.com |
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924RACR
Joined: 29 Jul 2001 Posts: 8816 Location: Royal Oak, MI, USA
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Posted: Fri Dec 02, 2016 11:06 pm Post subject: |
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It sat for nearly 4 years while I built a racecar... _________________ Vaughan Scott
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'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype |
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924RACR
Joined: 29 Jul 2001 Posts: 8816 Location: Royal Oak, MI, USA
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Posted: Sat Dec 03, 2016 10:03 pm Post subject: |
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Mixed results. Cleared 'er out and went for a spin yesterday after work.
Ran perfectly fine while cold/warming up - normal throttle response, good power and torque, no missing, idling fine.
Once she warmed up fully (warm idle oil pressure 2bar or below), then she dropped a cylinder again.
Gonna do some investigation this morning - check plugs, see if she runs properly again once cold, and maybe see if I can isolate something stupid like a bad plug wire. REALLY seems electrical. Plenty frustrating, but... here's hope.
Oh, yeah, added data point (for those following along and trying to diagnose)... while warming up and running well, the WBO2 looked fine - 11-13's. Once she started misfiring, numbers were very lean, up to 15-16+.
Not sure if that's due to the sensor getting raw fuel dumped on it, or if it's an indication of the CIS suddenly screwing up... _________________ Vaughan Scott
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'82 931 Plat. Silver
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morghen
Joined: 21 Jan 2005 Posts: 8886 Location: Romania
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Posted: Sun Dec 04, 2016 1:31 am Post subject: |
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CIS is probably fine, you're getting a missfire on one of the cyls. Replace the rotor, the cap and the wires as well as the plugs and try again. _________________ https://www.the924.com |
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924RACR
Joined: 29 Jul 2001 Posts: 8816 Location: Royal Oak, MI, USA
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Posted: Sun Dec 04, 2016 6:25 am Post subject: |
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Yep, and that's kinda where I'm headed now. General running is very close, with mild intermittent misfire getting worse with heat.
Some goofy wiring issue, or one of the controllers is going (DITC or the fender ignition module)... Close, almost fine, just not quite. Frustrating to have to put her away for the winter like this, but yeah. At least I got lots of heat run through her, and changed in some Mobil 1... _________________ Vaughan Scott
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'82 931 Plat. Silver
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morghen
Joined: 21 Jan 2005 Posts: 8886 Location: Romania
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Posted: Sun Dec 04, 2016 4:36 pm Post subject: |
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Well you can still start it up and do work even if its winter. _________________ https://www.the924.com |
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924RACR
Joined: 29 Jul 2001 Posts: 8816 Location: Royal Oak, MI, USA
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Posted: Mon Dec 05, 2016 12:02 am Post subject: |
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Yeah, 'cept I won't be around. And then she'll be buried under snow, at least after Christmas. Plus of course there's a more urgent project car needing much more work... still gotta build up a spare motor, build a new front clip from scratch, redesign the fuel system, and a few handfuls of smaller items... when I'm not out of town working on fast cars... _________________ Vaughan Scott
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'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype |
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924RACR
Joined: 29 Jul 2001 Posts: 8816 Location: Royal Oak, MI, USA
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Posted: Mon Dec 05, 2016 5:52 am Post subject: |
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I think we got progress. Raided the off-site stash of parts, found some good bits to swap in.
Wires didn't make a real difference.
Then I swapped in the spare ignition unit (fender-mount, not DITC controller). Definitely that. Runs pretty clean now, none of that popping/stuttering.
Still have some sputtering if I go off-throttle at high revs (5krpm or the like), such as from a downshift - think I'm sucking oil through then, either valve seals (hope not, they're pretty new!) or the turbo seals (likely, due to age). But I don't normally drive like that, and if I avoid that everything's clean.
Still probably want to swap new plugs in, and she needs a few other things besides... guess I'll be calling Dan before long, putting in an order...
Very happy 'bout being able to put her away for the winter like this... thanks for all the positive thoughts... let me know how much I owe ya for the chickens... _________________ Vaughan Scott
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'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype |
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morghen
Joined: 21 Jan 2005 Posts: 8886 Location: Romania
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Posted: Mon Dec 05, 2016 6:26 am Post subject: |
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Its a good feeling when you can find and fix things like this before deadline.
Cheers! _________________ https://www.the924.com |
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924RACR
Joined: 29 Jul 2001 Posts: 8816 Location: Royal Oak, MI, USA
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Posted: Mon Dec 05, 2016 7:16 am Post subject: |
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Yup!
I had previously removed the electronic component from the heat sink to clean off corrosion. Perhaps I didn't use an appropriately conductive material for the reinstall to the heat sink... _________________ Vaughan Scott
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'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype |
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