Strange misfire cured!

[malcolm]

Recently, my car started running on 4/5 cylinders on a journey, then cured itself. Then happened again temporarily. I suspected my (old) HT leads, but decided to change everything; that way I could keep the old stuff as spares in the boot in case of breakdown (at least I knew it all worked to a degree)
So, new HT leads, new plugs, new coil, new dizzie cap, new rotor arm and new "powerspark" electronic module that sits in my standard dizzie.
It ran beautifully until under heavy acceleration when it hit about 4200 revs when the engine would die! Never had that before. I suspected the new coil maybe, and changed it, but same problem everytime I hit those revs. Checked everything, including timing, and all seemed perfect. The car continued to run beautifully until that magic rev limit.
I then suspected the new powerspark unit, but before replacing it with the old one, I rang them up. Helpful chap spoke with the boss, then asked me "do you have normal copper HT leads?" Yes I said, but I had them with the older powerspark unit as well. He explained that the newer units are better, but more sensitive, and need to run on silicon leads. The field from copper wires upsets the unit.
They made me up a set of silicon leads to measure, with caps, and sent them to me for £29.95 inc. postage, AND threw in a new powerspark unit with red rotor arm in case I'd damaged the other one for free! - a bargain I think. Fitted them, and the car is now perfect. Ran it up to the red line in 3rd a few times with not a cough or splutter. Ticks over like a dream. So, a lesson learned.
Just thought it may be useful info for others with these sort of units if they have problems.

[Hugo]

Now you know why I don't like electronics! Did you see my post about the Powerspark distributor I fitted to my wife's Morris Minor (morris Ital 1275 engine)? When I tried to start the car, it would kick back violently - and I mean violently! I thought it was going to break the crank. Somebody suggested - and this is the only theory I have really - that the starter motor right next to the distributor was throwing out some 'fields' or something that was triggering random sparks. It would start perfectly on the handle, and it would run perfectly, but if you could get it to turn over at all on the starter it was frightening!
They sent me a second distributor F.O.C. which was just the same, so I went back to good old points!

[Hugo]

[quote="malcolm"]

.....He explained that the newer units are better, but more sensitive, and need to run on silicon leads.... [end quote]

That is an oxymoron is it not?

[malcolm]

Probably Hugo! Think they meant it was more efficient provided you have the right ancillaries to go with it. Can't argue with the service though!