car shuts off for half a sec then turns back on.

[Calypso Moor]

over the last two weeks this has happened a few times.
I'm driving and the car cuts out/jumps/shut off for half a second then goes back to normal, as far as I can tell the dash light and radio stay on but everything else goes dead.
I don't even know where to start looking for the problem.

[nando]

check your main relay. the main relay turns on the ignition system (DME, coils, etc), the radio etc. are powered separately.

I had the same thing, the weird part was my Megasquirt still got power somehow (maybe the capacitors had enough juice to power it for a second), so I could datalog when the power would shut off, which is why I never suspected the relay. I'd push down the throttle and nothing would happen. I chased that bastard for 2 years, replaced all sorts of expensive shit and it was a $5 relay. !@#$^!!

at this point, don't trust 25 year old relays. I'd replace all 3 of the engine related relays - the main relay, fuel pump relay, and O2 heater relay.