Ok Detectives, Unusual Problem

[Craig]

I need some help on this one.
Some time in the last 3-4 weeks my car has developed the unsettling habit of the engine shutting down, and then turning back on, all while cruising at speed.
I was cruising along, doing about 65 mph, and the engine just shuts off, and then starts back up a second later (did not even have to pull over). On startup, there was a back fire, and then everything was fine. Just prior to this happening, the car did not cough, hesitate, lurch, jerk, spit, sputter, or anything else that would indicate a problem. Upon the restart, just the back fire, and then the car runs just perfect again, no cough, hesitate, lurch, jerk, spit, sputter, or anything else. Runs and accelerates just fine, no loss of power before or after this event. This happened 2 times during this cruise. It was at night and the headlights did not flicker or go out, and there were no other signs of any thing else electrical related. I mention the headlights because if the headlights are left on when the ignition key is turned off, the headlights will go out (parking lights stay on), so it does not seem related to this circuit.
I am leaning towards an electrical problem somewhere because of the backfire on restart, seem like there is unburned fuel when it restarts.
I have jacked up and crawled under the car to check connections at the starter, and the ground strap, all very good, no corrosion, etc. I have checked connections at the CD unit, the battery, all the fuses, and the fuel pump; again all very good with no corrosion. I'm stumped!
Has anyone else had something similar? Is this the symptom if a specific part going bad, like the CD unit or something, and I just don't know the symptoms?
Any help will be appreciated!!!! I will try to keep up with responses to this, but your patience is appreciated...
Craig
77 911S, 2.7 CIS

[marcesq]

Have you checked the condition of the rev limiter on the rotor and the condition of the distributor cap ??

Also, is your coil leaking any oil??

I would concur that you should look for an electrical problem first since I believe that a fuel problem would result in some coughing and weasing when the car shuts off.

Hope this helps.

[widebody911]

The very sudden cutting out sounds like ignition. I had this with my '77, and ended up having to replace the wires between the coil, distributor and CD box - they'd just deteriorated after 20-something years. The wires broke inside the insulation, but gave no outward appearance of defects. Found it by testing them for continuity.

[nhromyak]

I had this problem with a 73.5T with CDI. Turned out to be a bad CD unit.

Check out...
http://www.pelicanparts.com/techarticles/mult_ignition_trouble_list/mult_ignition_trouble_list.htm

Good Luck.

[jwetering]

and of course check the "infamous green wire " You'll have to search to find the thread.

The wire leads to the base of the distributor...I don't know what it does, but I imagine it either provides power to the dizz, or some kind of reference current.

I got scr*wed by this little bugger once - it's a co-axial wire, and the inner sheath of insulation had cracked. The wire was shorting out, but you couldn't tell by looking at it.

I replaced a fuel pump before I figured it out. Almost replaced a CD too - don't replace the CD until you verify it's this wire.

[Superman]

Fuel supply problems on injected cars can act just as sudden as this, but I agree this is not your problem. Based on the backfire, I'd say there is no question but what your ignition system is intermittently shutting off and then back on. In noticing that other electrical stuff is not changing at the same time, you have ruled out a number of things, like battery connection. I doubt it is your ignition switch, for this same reason but it still could be I suppose.

The folks above have identified the areas I consider most likely. Broken or shorted wire, or CD box. I'd test all the wires individually with an ohmmeter, first thing.

[91C2wrencher]

From the FWIW Dept. Although my car is newer '91 C2, I had similar problem this past summer. Turned out to be one or more VERY loose spark plugs! Wierd? yes, did retorquing them fix the problem? yep! smell fuel? where does fuel come from? from inside the cylinder and out the plug hole?

[Craig]

Hey Guys,
Thanks for the replies so far.
Marc - I did check the coil and dist, just forgot to mention in the haste to post. Coil looked good (never heard of one leaking oil, that is new to me), but all connections good. Dist Cap looked good, just looked at the rotor under cap. I did not remove the little 'cover' that sits just under the rotor blocking the view to everything else, I will look under the 'cover soon. I don't really know what the rev limiter looks like, but I will look for anything out of the ordinary.

Thom - I really was just surface checking wires and looking for obvious signs,bad connections etc. I do not really know know how to check for continuity. (I am not a big electrical guy, I would rather work on things mechanical, and don't have any testing equipment). Sounds like a good check to look into though.

Nick - When your CD box went, did it do these same things? Or just not start/run at some point?

Jasper - Green wire, eh? I will look around the base of the dist, and see if I can even find it! When I get the time later, I will try searching on the threads.

FYI, the car hasn't done this for 2 weeks now. I have gone on long drives, revving up the engine to 5500-6000 before shifting or shifting around 3500 just to try to vary engine load, jiggling wires under the dash, jiggling the key, etc just to see if I could do some thing that would cause to to happen, but nada.
Thanks for the suggestions so far!
Craig
77 911S, 2.7 CIS

[Superman]

I think the wires you would need to jiggle would be near the distributor or CD box. If it were me, I'd very definitely use an insulated plier or screwdriver for this. Upwards of 50,000 volts!

You test continuity with an ohmmeter. I also don't know much about electricity, but I know you should go to Sears or someplace and get a decent ($60 perhaps) automotive multitester. It would include RPM, tach, dwell and an ohmmeter.

Yes, bad coils can dribble. Silvery stuff.

[nhromyak]

Uh oh. Now you asked. 73.5 T CIS 2.7 motor back in 1987.

Mornings (cold)- The CD whines... the car does not start. Go check things out.. Jiggle wires. ... Still no start. Come back in five minutes. Fired right UP!

OK
Now I am driving all is well one day.
next day I am driving in the morning - drive about 2 miles - dies for about 1 second then it FIRES right up again! WTF?

For a while there it happened at the same EXACT spot for three days straight. I thought I was going across some sort of high powered EMF killing the ignition.

Then one day I passed that spot with no ignition problems. Then I had intermittent problems, and other weeks I had no problems.

Anyways, I found the permatune guy who lived nearby by me. He was working out of his garage at the time. He had EVERYTHING in his garage. He hooked it up, and saw on his Scope that something was amiss on the BOSCH CD unit.

Sold me one of his for ~$150. I didn't have a problem since.

Bottom line - after checking all the other electrical items out (especially the green points wire) get the CD checked out by someone who can check it with a Scope.

Usually, the BOSCH units don't have any problems. And when these do fail, you no longer hear the whine.

Good Luck.

[antares]

Now you said it...mine is doing the same thing.
Be driving and it is as if someone reaches over and just turns the key off. Engine dies and then if you don't immediately get off it, there will be a back fire. It did this a couple of times when I was out driving. Then one day while it was idling it just quit. Now it just refuses to start. Got to check everything. I have a PermaTune and they do not whine like the stock units do.
Antares

[Leland Pate]

Man if only I could tell you... I had this EXACT same thing happen to me a couple years ago.
I remember it so well because it was the one problem that I've had with my car that I just couldn't fix myself.

Here's what happened...
Me and the girlfriend are driving back to base at about 65mph...everythings fine....just cruisin'... then all of a sudden....brrrrrrrrrrrr r r r r r r r ...it was like someone reached down and turned the key off.
I rolled to a stop with a very confused look on my face... it cranked and cranked but no spark. So I go through the usual...check cap, check rotor, plug wires, coil, CD unit...everything seemed to be in working order but I was still getting no spark. I even went as far as replacing the CD unit and coil...still no spark.
Totally defeated, I had the car towed to my wrench...who worked on it for a week...thinking that it was somehow related to the ingnition switch or something, I think.
Anyway, one day I stop in to see if he had made any progress... So, I'm chatting with him in the break room while one of his apprentices was looking at the car again. All of a sudden I hear a "VRooooooooooooooooooM!!!
I instantly knew it was my baby! Dumbfounded, we both went to have a look; there was Chris (apprentice) with a beaming smile on his face. I said "What did you do!!!???"
He just shrugged and said "I was just going through the fuse box, cleaning and tightening the screws...your right headlight high beam fuse holder was lose....so I tightened it and tried to start it again."
Well son of a ..... I still have no real clue as to WHY this worked...but ever since then I have not had a problem.
(This was before I knew about the Pelican board)
I should also note that about a month later, the brand new Bosch coil I bought from Perf Prod. "soiled it's pants". I was irate.
They refunded my money and I ended up putting the old coil back on...no problems since.
And yes, they can leak coolant...that's what happened to mine,... if you shake it you should be able to hear it slosh.

Best of luck....damn electrical gremlins can be a bear!

[cary]

My .02c for today.

We must remember these cars are expirenced ( old ). One of the best projects for the long term enjoyment of your car. Is to change out the fuse blocks. Taking time to inspect and clean every connection was a soft copper brush. Making a new connection. Then replace every fuse.

Might be off a bit, but $50 max.

If you can wiggle the wires and or twist the fuse to correct your electrical problems. You need to do some connection refreshment.

Unless you like standing on the side of the road with that dumb look on your face.

[Leland Pate]

Well, I wouldn't necessarily say it was a "dumb" look....
..."sadly confused"... maybe...
..."Totally lacking in understanding"......possibly...
...but definately not "dumb".

Good advice from my Northern friend... I learned my lesson.

[cary]

My .02c wasn't pointed at anyone. Leland or Craig.
Dumb translated into : This car IS really pissing me off !!!

Just a general input. I hate chasing "ghosts". ( electrical problems that come and go ). I'm at the point now, everytime I "touch" an electrical connection I clean and tighten it.

" An ounce of prevention, is worth a pound of cure ".
Once again .02c.

Out to the garage for some prevention. The door locks on my new 914 get almost un-usable when it gets below 20 degrees. I can see me breaking off the key. Then I would have that dumb look on face.

I'm going tear the doors open and take the latches out and clean them. Getting any and all grease ( old & wet ) out of them. Then relube with that "door ease" graphite stuff.

Leland, 40 degrees and a Big Sky Day.

Craig, do a search on Permatune and or CD. Seems a year or so ago, a couple guys were chasing that same critter. If not here, try Rennlist.

[Leland Pate]

[Craig]

Thanks for the replies guys!
Leland - LOL at your response!
Cary - No offense taken. How can I take any when I certainly have the 'deer in the headlights' look about this one. I did look over the fuse box to look for blown fuses or bad/loose connections. Not a bad suggestion to create a 'new connection'. I will give that a shot.
Superman - I know I should get the multitester. I just haven't because then I would feel like I have to use it . Seriously I think I will get one, could certainly use it for both my cars.
Nick - thanks for clarifying your problem, it does sound exactly what I am going through.
Antares - any progress ?
Since there are several posts about the CD box, I will get it checked out. Mine too is a PermaTune, so there is no whine to check for. (Thought I was going deaf at first )
I will update when I get some news!
It has been said before, but THIS BOARD ROCKS!
Thanks for all the help so far!
Craig

[jp88targa]

Craig ,
I had a similar problem with my '76 2.7.
Doing the same things as the others I had no luck but I did get a few ZZZs in the trunk. I found the plug connection on the back of the ignition switch came loose. I removed it and cleaned it, replaced much better , problem gone.
Good luck with yours. JP