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Pray for the '82 931...
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924RACR  



Joined: 29 Jul 2001
Posts: 8036
Location: Royal Oak, MI, USA

PostPosted: Thu Dec 01, 2016 11:49 pm    Post subject: Pray for the '82 931... Reply with quote

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...
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Vaughan Scott
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'79 924 #77 ITB racecar
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Fasteddie313  



Joined: 29 Sep 2013
Posts: 1418
Location: Not Detriot - NMI

PostPosted: Fri Dec 02, 2016 2:47 am    Post subject: Reply with quote

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?
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Rasta Monsta  



Joined: 12 Jul 2006
Posts: 11332
Location: PacNW

PostPosted: Fri Dec 02, 2016 3:40 am    Post subject: Reply with quote

Psst. . .Vaughan is an engineer


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924RACR  



Joined: 29 Jul 2001
Posts: 8036
Location: Royal Oak, MI, USA

PostPosted: Fri Dec 02, 2016 5:36 am    Post subject: Reply with quote

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.
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Vaughan Scott
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'79 924 #77 ITB racecar
'82 931 Plat. Silver
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924RACR  



Joined: 29 Jul 2001
Posts: 8036
Location: Royal Oak, MI, USA

PostPosted: Fri Dec 02, 2016 9:20 am    Post subject: Reply with quote

Soaking in mysterious oil now... jiggled it back and forth a few... fingers crossed for improvement tomorrow...
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Vaughan Scott
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morghen  



Joined: 21 Jan 2005
Posts: 7674
Location: Romania

PostPosted: Fri Dec 02, 2016 6:42 pm    Post subject: Reply with quote

how can you clog the injectors? i dont run my cars for 6 months or so and they start at quarter key every year.
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924RACR  



Joined: 29 Jul 2001
Posts: 8036
Location: Royal Oak, MI, USA

PostPosted: Sat Dec 03, 2016 12:06 am    Post subject: Reply with quote

It sat for nearly 4 years while I built a racecar...
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Vaughan Scott
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924RACR  



Joined: 29 Jul 2001
Posts: 8036
Location: Royal Oak, MI, USA

PostPosted: Sat Dec 03, 2016 11:03 pm    Post subject: Reply with quote

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...
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Vaughan Scott
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morghen  



Joined: 21 Jan 2005
Posts: 7674
Location: Romania

PostPosted: Sun Dec 04, 2016 2:31 am    Post subject: Reply with quote

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.
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924RACR  



Joined: 29 Jul 2001
Posts: 8036
Location: Royal Oak, MI, USA

PostPosted: Sun Dec 04, 2016 7:25 am    Post subject: Reply with quote

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...
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Vaughan Scott
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morghen  



Joined: 21 Jan 2005
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Location: Romania

PostPosted: Sun Dec 04, 2016 5:36 pm    Post subject: Reply with quote

Well you can still start it up and do work even if its winter.
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924RACR  



Joined: 29 Jul 2001
Posts: 8036
Location: Royal Oak, MI, USA

PostPosted: Mon Dec 05, 2016 1:02 am    Post subject: Reply with quote

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...
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Vaughan Scott
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'82 931 Plat. Silver
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924RACR  



Joined: 29 Jul 2001
Posts: 8036
Location: Royal Oak, MI, USA

PostPosted: Mon Dec 05, 2016 6:52 am    Post subject: Reply with quote

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...
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Vaughan Scott
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'82 931 Plat. Silver
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morghen  



Joined: 21 Jan 2005
Posts: 7674
Location: Romania

PostPosted: Mon Dec 05, 2016 7:26 am    Post subject: Reply with quote

Its a good feeling when you can find and fix things like this before deadline.
Cheers!
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924RACR  



Joined: 29 Jul 2001
Posts: 8036
Location: Royal Oak, MI, USA

PostPosted: Mon Dec 05, 2016 8:16 am    Post subject: Reply with quote

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...
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Vaughan Scott
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