Battery to starter cable fault
 

I have what appears to be a faulty cable from the battery to the starter. It's been turning the engine over slower and slower until finally I had to investigate. Wiggling the end of the cable at the starter appeared to fix the problem for now.

I will renew the cable ASAP. But meantime could this also be the cause of a general lack of power? At the same time as the starter began churning slowly, the engine seemed to have no real 'go' on the open road. Is that possible?

check the ground cable too, there should be one between the frame and the engine block as well, I've seen starter cables burn out before, not real common but it happens.

Possible depending on the vehicle. At least on mine, the starter is acts as a junction block as well. The alternator cable goes to the starter, then goes to the battery. So if that cable was bad, the battery would run down, and it would run worse due to low voltage problems.

Cleaning all your grounds/connections should help. I've never heard of a cable being bad, just rust/oxidation on connections

It wasn't the main battery cables after all. It appears to be the wire frm the 'M' terminal into the starter itself. Of course I can *see* it but can't reach it without some major dismantling...