I made the mistake of cleaning my engine bay (didn't jetwash it however
) and got a terrible misfire. I got water into the spark plug wells and I thought I'd ruined my spark plugs as they had gunk all over them so I bought brand new NGK plugs which didn't fix it. Then I thought I had injector trouble. Turned out to be moisture in the HT leads which over time dried out while I was trying to diagnose the issue and the car fixed itself! so try your best to dry the leads out along with the coil pack