EJZero1

86 951 w/ M-Tune, new fuel pump, filter and lines. New tune up. All done late last year. Just took the car out of winter hibernation a few weeks ago. Was running great until sudden onset of symptoms.

Left work on the way to a social engagement last night. 5 minutes from work, just died at a red light like the key was turned off. No stumble or stutter. Just turned off. Started right up again, but idled for just a few seconds and died again. Cranked, back fired, started again just long enough to get me across the intersection before dying again. Started again. After checking under the hood as it kept idling, everything looked and sounded normal. Got in and completed the 20 minute drive, albeit gingerly.

Tried to drive home about 3 hours later and same issues arose. Backfiring, idling for a bit... When she would stay running long enough for me to try to get moving, it would cut off before I got more than a couple of hundred feet.

While idling long enough for me to cycle through the Zeitronix parameters, AFR's and vacuum looked normal.

At this point I thought it best to just call for a tow and check things out when she's safe in the garage.

After doing some reading, here's my initial short list of things to check:
Timing skip a tooth or two? Check for TDC
Rotor loose?
Vacuum/IC coupler loose or split? But vacuum looked normal?

Here's to hoping it's quick and easy. (Who am I trying to kid here?!)

Turbodan

My guess is rotor either loose or dirty.
good luck. I hope it works out.

EJZero1

Just checked my short list...

Rotor is tight and appears clean, reflective of a few hundred miles since installation.
Timing is spot on.
IC couplers appear good.

When cranking last night, I checked for tach bounce. Tach was actually jumping towards 2-3k while cranking.

Time to do more reading.

Open to guidance!

V2Rocket

check ignition switch function and also check for 12V constant at the ignition coil black wire.


*edit* jumping to 2-3k isn't normal, it should move maybe 1/16" or so, maybe enough to hit "200 rpm" mark...unless you've got the highest-output-voltage reference sensor in the world

EJZero1

I thought the large tach jump was unusual, too. Any idea what that might point to as a potential cause?

Thinking back to yesterday, it seems that time from start up to onset of symptoms was pretty close in duration. Maybe about 5 minutes drive time. Coincidental, or possibly the issue is one that results from a certain temp gain? Maybe when I get some more time I'll start it (assuming it does) and just let it idle for a while to see if it "times out" and dies.

Thanks again.

thomasmryan

do you think the coil or the Zeitronix ZT2 is back feeding the tach?

V2Rocket

...without going into too much detail as to why, try putting your MAF power wire on a source other than the ignition coil and see how things change.

951Dreams

If it was me, fuel would be an item high on my list. Not if it keeps to the 5 minute thing, but if it's random... We'll, with the symptoms....

But really that tach thing gets my attention, as V2 said that ain't normal. If it was me the electronics would be my first concern, fuel then spark. But then, V2 has forgot more about these cars than I'll ever know, so there's that lol.

bw993

Find a different +12V for the M-tune MAF. The 12V from the ignition coil is way too noisy. I would check your BOV, since your car behavior sounds like it may be leaking.

cruise98

Check the connectors on the speed and reference sensors too.

Make up a 3 way connector or have a spare "known to be good" DME relay to swap out when the fault happens again.

EJZero1

Thanks to everyone for all of the great inputs!

In the past I've noticed electrical tape at the connections for the speed/reference sensors. I think for starters I'll replace both. I may have a spare DME relay in the garage for checking at the next instance, as well. If not, I'll whip up the 3-wire jumper as suggested.

All of this will have to wait til after the weekend, but thanks to your suggestions, I've got a few more things to check.