Unknown type of engine failure

[bugstrider]

Ok,

I understand this may be a little odd as far as my initial approach to diagnosing an engine problem but I'll give it a try anyway. I am in the beginning phase of trying to understand what has occurred so bare with me.

Last night while on my way home, I noticed what I would describe as a slight whirring noise. It was one of those deals where you think to yourself, "that sounds a little off, wonder what that is". Literally, this was a just two minutes before the car did what it did.

As I pulled onto the road leading to our house, the car made an unusual pop or pharumph sound, then started to run really bad. RPM's dropped off, no power, barely could get it to idle really jockeying the gas peddle. The charge light and E-brake light came on, then it died. Popped the deck lid and could smell a slight oil smell and since it was at night, slight smoke could be seen in the beam of the flashlight. It was a warm night and temp was sitting at its usual spot on the gauge and had good oil pressure per the gauge as well. Course start the engine but it would lope and then die. Here is a link to the way it was running.

http://youtu.be/wr4xF-mkqPU


After approx. 30 minutes the car was able to start and keep running.....just barely so I went for it and drove it home less than a mile away. Dealing with AAA for a tow that short of a trip and to be honest, they were such a pain in the A$$ I really wanted to punch them through the phone.... Lol

On e home, it continued to run really bad but it still idled. Here is a link to it's idle.

http://youtu.be/kIrmwteNegQ

So here is my query to the groupe. Just by watching the small clips, has anyone experienced this or have any suggestions? At this point, any would be helpful......

Thanks

[E Sully]

Possible tensioner failure causing timing chain to skip a tooth.

[johnsjmc]

You again LOL How many miles on it? Have tensioner,s been updated to Carrera style? since you risked driving it a mile then .
You can try running it briefly and feel the exhaust pipes where they exit the heads underneath. They should all be equally hot to touch if all cylinders are firing even if cam timing has jumped. Next pull the plugs, look at them and do a compression test. If cam timing has jumped it should show big difference in compression each cyl.

[silverc4s]

If the timing jumped a tooth on a cam, I don't thing waiting 30 minutes would make any difference. Heat related sounds more like a bad ignition coil, or some CIS malady to me.
Do you have a CD Ignition box? Can you hear it humming?

[bugstrider]

No CD ignition box but I do hear a whine when I kick the ignition switch on.

As far as running 30 minutes after is shut down, running being used in the loosest of context. It was just hanging on by a thread. The drive home was in 1st gear only because had I made the gear change, I'm positive it would have stalled out.


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[johnsjmc]

My point about running it. Is if it has jumped timing it might already have bent a bunch of valves. A compression test will say for sure I wouldn,t drive it anywhere and would be unsure if I would run it at all until I at least pulled the plugs.
Basic auto shop: An engine only needs 4 things to run a combustible mixture, compression ,a source of ignition, AND everything needs to happen at the right time.

[timmy2]

From the initial symptoms I would pull the fan belt and then spin the fan and alternator to see if there is a problem there. If all seems normal then I would suggest you drain the oil through a cloth strainer and look for metal. (Checking the drain plugs as well)
Then pull the valve covers and look to see if a rocker shaft has worked its way out.
Check the cams for missing pieces, check the rocker covers and areas for metal shavings, pieces look at valve springs etc.
Take a look at your distributor and rotor as well. (Rev limiter?)
Then if you find nothing it is probably time to look at the timing chains.
Just my 2 cents.
Good luck, I hope it is something simple.

[TCracingCA]

I would fire a timing light at it, if you know where that was prior to the incident. The usual compression check, then pull the valve covers, etc. I would drain the oil and check that with a magnet for metal debris, take whatever filter you have and cut it apart and inspect, etc. etc. etc. Basically all of the easy things to get a better overall picture!

[johnsjmc]

A rocker shaft could have worked loose , and you could also have a broken valve spring (but they will usually idle better than rev with a broken spring) BUT its easier to do a compression test by pulling plugs than to pull the valve covers. An inductive timing light will tell if the plugs are firing so will feeling the exhaust pipes where they exit the lower part of the heads.
If you find a cyl or cylinders with little or no compression. Then pull the valve covers for those cylinders. If all looks good under the covers , then drain the oil and cut open the filter etc because the problem will then be deep inside. Hope not.

[porsche930dude]

sounds like it was cranking super fast without much compression. so i would check that out first and have a look at the rockers and springs. Maybe you can tell which side by the clatter

[DaddyGlenn]

You (we) need more information. Do everything suggested so far that doesn't require starting the engine. Then report back.

We can all throw darts at a board and guess what it might be. More investigation will get us closer to the correct answer.

and really, don't start it again.

[bugstrider]

Inspection to soon start. I am fearing the worst but really trying to remain optimistically hopeful......

A sad day indeed.


At least the local tow driver from GnO here in ElDorado Co went above and beyond on this call. Ours was his second Porsche transport of the day and he really worked his magic since the front had been lowered.


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[bugstrider]

Originally Posted by porsche930dude

sounds like it was cranking super fast without much compression. so i would check that out first and have a look at the rockers and springs. Maybe you can tell which side by the clatter

Yeah, that little nugget jumped out at me as well. Doesn't bode well I'm afraid. Plug removal and C-check to follow.


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[bugstrider]

Originally Posted by johnsjmc

A rocker shaft could have worked loose , and you could also have a broken valve spring (but they will usually idle better than rev with a broken spring) BUT its easier to do a compression test by pulling plugs than to pull the valve covers. An inductive timing light will tell if the plugs are firing so will feeling the exhaust pipes where they exit the lower part of the heads.

If you find a cyl or cylinders with little or no compression. Then pull the valve covers for those cylinders. If all looks good under the covers , then drain the oil and cut open the filter etc because the problem will then be deep inside. Hope not.

That was my initial thought after I thought about it. With what sounds like total chaos going on in the video who know what I will find.

Didn't think about the oil drop and filter cut until it was mentioned in these replies. I was blindsided by the initial "Oh $h\t" factor. I'm sure it would have occurred to me to do that. Probably wouldn't hurt to send a sample out for analysis. However, at 262K, I'm sure it would resemble a smelting foundry.

Well, I guess my suspension mystery is not a big deal anymore.


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[bugstrider]

Originally Posted by timmy2

From the initial symptoms I would pull the fan belt and then spin the fan and alternator to see if there is a problem there. If all seems normal then I would suggest you drain the oil through a cloth strainer and look for metal. (Checking the drain plugs as well)

Then pull the valve covers and look to see if a rocker shaft has worked its way out.

Check the cams for missing pieces, check the rocker covers and areas for metal shavings, pieces look at valve springs etc.

Take a look at your distributor and rotor as well. (Rev limiter?)

Then if you find nothing it is probably time to look at the timing chains.

Just my 2 cents.

Good luck, I hope it is something simple.

Thanks,

Will check into all of that.


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[bugstrider]

Originally Posted by johnsjmc

My point about running it. Is if it has jumped timing it might already have bent a bunch of valves. A compression test will say for sure I wouldn,t drive it anywhere and would be unsure if I would run it at all until I at least pulled the plugs.

Basic auto shop: An engine only needs 4 things to run a combustible mixture, compression ,a source of ignition, AND everything needs to happen at the right time.

The timing chain jump is the major concern. When it first occurred, I was focused on a fuel supply or ignition issue. Completely overlooked the possibility of the timing jump risking valve damage and such. This is a prime example of inexperience trumps common sense.


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[johnsjmc]

With 250K on it if it hasn,t had a top end rebuild with new chains and guides it,s likely time.
car looks good and is worth fixing. As an aside to a previous post There isn,t a rev limiter in the distributer unless it,s a ROW car. The US SC uses a fuel cut relay behind the dash to rev limit.
You still might luck out and find something else.
It,s very hard to diagnose an engine failure by forum postings and youtube video,s

[johnsjmc]

Any cause discovered yet? Curious.

[bugstrider]

Thanks for checking in,

Well, I just talked with a good friend who is helping me with the engine problem. I can honestly say that I am surprised as to the cause of the chaos. It would explain the intermittent whirring sound, engine shutdown, then it to run enough to get home while running on less than six cylinders.

As it turns out, I wasn't too far off my initial thoughts of it being fuel or ignition related. I guess my distributor grenaded internally. Literally fragmented into shards of internals. My friend who has 40 years of Porsche experience said he has never seen one come part like this one did. Welcome to my wold, my first dog's name was Murphy. This was because the unusually seemed to follow my A$$ around at all times.

I honestly was preparing myself for the news of a needed overhaul. Now the challenge is going to find a replacement or check into a digital unit. I am not sure if these things are made on unobtanium on the 78-79SC.

Cheers Trevor

[DRACO A5OG]

Yeap my 3.2 dizzy whirled and caused miss-fires. Tried to rebuild it but the internal snap in bearings are not replaceable, I could have but one but elected to buy a known good one. So as long as the those internal bearings are intact, you should be able to rebuild a CIS dizzy.