2001 missing when wet

I have a 01 prerunner with a 3.4 that misses after a rain, just sitting in driveway.I have code po300 and misfires on cy4 and 6. If i spray coils down with water it will happen, If i spray plug wires down it wont. What is the chance i have 2 bad coils? Trucks has 178,000 miles and runs great other than this new issue. The miss goes away after a couple miles. Thanks for any help.

 

If those are the factory coil boots then there is a good chance that is your problem . My guess is you coils are good , your coil boots not so much . At 178K I would replace all the coils , which would also replace the boots . If you replace the boots alone they can be had for about $30 from Amazon.com, Denso 671-6248 is the factory boots,they can't be bought from a dealership as they only sell the complete coils. The O.E. coils are Denso 673-1201.

 

If it is a coil boot how come the misfire is on the other bank?

 

Swapped 5 coil with 3 and spayed them light didnt come on but my scanner has po 300 code. It didnt miss long enough to post a clylinder. Never have a problem running down the road only after sitting with rain.

 

I had this code recently when it rained. (don't know why since nothing is wet underneath the hood) but I used dielectric grease in the boots and it seemed to have solved the issue.