'99 Toyota Corolla running rough with check engine light

I got this customer car that he/she bought a couple days ago from our dealership. The complaint was the car runs rough sometimes and the check engine light is on.

The first thing I did was to check what was the codes that brought up the check engine light. I had a feeling it was a misfire code. I was right!! The codes were P0300 random misfire, P0302 cylinder#2 misfire and P0303 cylinder#3 misfire.

Next step I did was to remove #2 and 3 spark plug and check the plugs visibly if its good. Both spark plugs looked fine. Then I looked at the ignition coil pack that was connected with #2 and #3 spark plug wires. The casing looked fine. So I decided to remove the spark plug wires that was connected to it and look inside where it connects.

I found the problem. It was water inside the plug wires where it connects to the ignition coil pack. #2 and #3 cylinders share the same coil packs so obviously it caused the misfire and check engine light on.

You might be thinking, how did water get inside there? Well, when it's sold, before the car is given to the customer it gets detailed from top to bottom, inside and out. When the detailer cleaned the engine bay he used the pressure washer to get rid of all the dirt. While doing that the ignition coil pack got wet.

What I did to clean the coil pack and both plug wires is to spray it with contact circuit cleaner and then air hose it dry. Then I plugged it back and went for a 30 mile test drive to set the monitors on the car.

Came back to the dealership with the car with no check engine light and no rough idle.

I'm fucken good!