Driving down the M1 today from Leeds to London, 85mph, outside lane and the revs drop to 0!!! for about a second - that can focus your attention I can tell you! and then the engine comes back to life perfectly. Pull over to the hard shoulder fearing the worst, turned her off, checked everything I could think of and nothing. Restarted and it and made it all the way home (150 miles) with no problems at all. Hoped it was just 'one of those things' but got home went back to the car after it had been off for 10 minutes and it would turn over but not fire up. Waited another 5 minutes and it started first time - went for a drive and repeated the process - would not start and then it would. My first thoughts were a loose connection but that really does not fit the pattern. Perhaps a fueling problem? Taking it to Mazda do get the diagnostics done next week but I am sure I have heard of something similar before, so any ideas? In case it helps, my car is a 1990 Mk1 (UK) with 100K on the clock. Fingers crossed... (7/00)
My friends Golf did this when she was on the motorway, all electrics died too...did yours...? I'm no mechanic so I can't offer any advice about oily bits, but the only thing I can think of is your battery terminals? (7/00)
No, I kept the electrics and the battery is fine, when it starts it fires up almost instantly...back to the drawing board!! (7/00)
For anyone who is interested in my mx5 problem, the current thinking from several people I have talked to over the past day or so is that it may well be caused by a fuel filter problem. I have had the car for 2 years and have not changed it and have no record to when it was changed before that, so does this sound likley for a inconstant fueling problem? Do fuel filters get blocked that often, anyone got any experience of this? (7/00)

I've joined in this one a little late and can't remember your symptoms, but a few years ago I had the following problem with a car that was cured by changing the fuel filter:

Car generally behaved as it was supposed to, except under sustained motoring (e.g. clear dual carriageway/motorway), it would start to lose power over a couple of miles, I'd pull over and could just maintain idle with my foot almost to the floor! I'd turn the engine off, leave the car for 5 minutes, and then start it up again. Everything would be alright for another 30 miles or so, and then the same would happen again.

Like I said, I changed the fuel filter and everything went back to normal. The car was an 'F' plate 323. (7/00)
They sound very much like my symptoms so hopefully the fuel filter that is well overdue for a change is the culprit. Fuel filters are a tad cheaper then new ECUs'!! Thanks for the help!! (7/00)
.as said .. they do block .. .. and ECU's tell you what is wrong .. go see that Donutz site for your prayers answered in paper.. (7/00)
I had something similar on a MkI Gti a few years back, turned out to be the relay for the fuel injection. After a good engine clean some water had found its way to the relay-box screwing up the fuel injection relay. Engine would cut out from time to time only to start up perfectly after a short while, indeed scary if this happens while overtaking a lorry. (7/00)
That problem could be caused by bad ground(s). The ground strip between engine and chassis (right behind the header) and the one close by would be my first suspects ... Check and clean them! (7/00)
I have just changed my fuel filter as part of routine servicing. Easy job, took about half an hour (with this being my first attempt). (7/00)

Just in case anyone is interested, my engine problem of last weekend has been solved by Tamplins. Got a call this afternoon telling me thay had repalced the fuel filter and cleaned injectors etc but they could not find any problems and were stumped. Guy went around the back to get the car and dissapeared for ten minutes, went around to find the car sourounded by mecahnics scratching their heads. The damn thing would not start!!!

Anyway, a light bulb appeared above the head of one mechanic who dropped the steering panel and disconnected the immobiliser and hey presto the thing started first time. I would never have thought that it was an intermittant fault with the immobilser!! Bet none of you thought of that either!! Fingers crossed it was that and stays running now!

Anyway, now I need a new immobiliser/alarm - I usually skip over those e-mails, so has anyone got any reccomendations. Mazda guy said he could fit an immobilser for 150GBP. Thanks to all who have offered help on this one, much appreciated! CHEERS!! (7/00)

I'm really sorry I didn't reply to your E-mail when i saw it, I was going to but just didn't seem to get round to it, Arrgh!

Anyway my car did this last Spring ('99), on rare occasions would cut out whilst driving or coming to a stop, just for a second and then recover or would just restart. Finally the car shut down in traffic and wouldn't start, imobiliser led was red and not green, so guessed the imobiliser at fault. Had it replaced and all is well.

BTW this was a Vecta (the new one isn't;-) and the guy who fitted it and then my replacement said that they get a rash of Vecta's doing this each Spring/early Summer as the temps rise. He no longer fits them, it would be unpleasant doing 80 in rush hour traffic if your engine shut down, yes? (7/00)
When my old immobiliser went on my five, the car would cut out whenever you selected reverse!! How long did it take me to trace this to the immobiliser?....Less than bloody obvious. Finally stopped working altogether and left me stranded with no tools. Argghh. (7/00)