My car was running fine this morning, very smoothly. Then after some rain, when I started the car I had a rough idle and acceleration. After a few minutes I got codes P1313, P0303, restricted performance and a flashing check engine light.

This is maddening. What did that rain do to my car? What can I do to fix it?

 

Firstly, you must eliminate the misfire in cylinder 3, and any other misfire(s).

Do not operate the vehicle under any conditions that cause the MIL to flash as catalytic converter damage is occurring!

 

I guess I'm walking tomorrow. How do I eliminate the misfire?

 

Remove the coil from cylinder 3 and inspect it for oil or water fouling. If there is water from the rainstorm in the spark plug well, it must be removed. If there is oil fouling, you must renew the cam cover gasket and spark plug boss seals for that side of the engine.

The diagram below shows the cylinder numbering scheme for previous and ISO designations.

 

Do not be surprised if you eventually have the P0420 DTC with the MIL on after you correct the misfires.

If that DTC does appear, the Bank 1 catalyst will need to be replaced.

 

I haven't driven the car since the problem appeared. I am almost certain it was water. My bonnet is not seated correctly due to a power steering pump service which called for removing it. That might have allowed water to enter the wrong places during yesterday's heavy rains.

 

There was a shocking amount of water condensation on the coils of the right bank. There was also a small amount of oil. I cleaned everything up and removed all the water and oil I could. However, the symptoms are still there without the CEL, restricted performance or the flashing CEL. The car feels better but it is still not smooth.