I had the same problem on my Zetec when I bought it. Just like your SVT, my Zetec would only die once in a while. My conditions were as follows:
clutch was always in
always rolling to a stop
RPMs always in idle range
It would act just like you turned it off, but the key was still in the "on" position.
I had the dealership put on the 15 sec. before/15 sec. after recorder. I must've gotten 6 records for them before I took it back. Guess what they told me..."looks like you just shut if off". Yeah, thanks, dickwad :rolleyes:
Anyway, the last time I took it in for this, I was told they found nothing, but the car never did it again. My guess is something involving the ignition system (loose wiring, perhaps) was noticed and they didn't wanna fess up. No amount of inquiries landed me an answer; they'd always just say nothing was ever found. Must've been one of those "under the table" repairs to save face.
My point is it almost has to be something the Zetec and SVT have in common. Doubtful it's mechanical because very little is shared between the two other than electronics (and chassis, of course). Good luck...hopefully you get an answer so I'll know what they did
