Possessed instruments

A month or so ago, my bug got mad at me: unexplained loss of power followed by a backfire loud enough to make my ears ring and bulge both ends of blow my turbo muffler out; shift light flashing like crazy, tach flying up and down. Fault lasted just a few seconds each time, but felt like minutes when in the middle of traffic! Other than this, no problems, engine runs just fine.

I figured this was down to the pro-control (which I have wired as a rev limiter, it's been on the car for several years) deciding I was overrevving and cutting power to the coil. But didn't know if the trigger wiring was at fault or the pro-control itself.

Not wanting to lose power in traffic again, I ran a short wire from the +12v supply at the pro-control directly to the n.c. terminal where I had the supply to the coil connected, effectively disabling the rev-limiter. If the problem still occurred, i'd see the effect on the shift light and tach, but not suffer the engine dying or backfire. I've had no problems since, so i'm thinking that the trigger wiring for the instruments is fine and something internal to the pro-control between the +12v and n.c. terminals was at fault.

This ring a bell with anyone..?

Just for my own interest, i'll pull the pro-control out of the car and take it apart to see if I can find any fault. I use to work on aerospace electronics so i've seen stuff damaged by vibration before, largely because it was my job to shake the cr4p out of things to see if they broke :-)