my 1989 4.9litre was running poorly ... missing all over the place; not fun to drive. finally got around to doing a basic tune-up on it and, to my surprise, it runs perfectly now. who knew that basic maintenance was so important ?

however, while removing the spark plug wires, 2 of them broke (i guess that's why they say to be careful when removing them ). the ones i had in there were 8mm and i replaced them with a couple of 7mm that i had lying around. should i be worried about frying my engines electronics ?

 

They broke? If the wire tugged off the boot, look in the boot. You'll see a little screw down inside. Push the wire back into the boot and twist so the wire threads onto the screw. Now stop tugging on the wires and just pull on the boot!

If anything actually broke, your wires are probably semi rotten and ought to be replaced.

As for the 7mm wires, I don't foresee an issue in hurting anything. Probably just have a little less current through the plugs with the smaller wires, so a little smaller spark, due to the slight increase in resistance of the wire.

Glad its running well for you again