Well High Pressure Water and old hoses, cables, & connectors really are not a good mix.
I fully understand the want to wash the engine down,,,done it in the past on other vehicles and always had an issue with idling or driving right after. From what I can remember it all just went away. Not saying that this is going to happen with your vehicle though.

I guess check all connectors, make sure all hoses on top are still plugged in before buying parts.

Good Luck and keep us posted.