My friend has an 04 RST Truck, 4.8 5 speed with a K&N cold air intake. The thing will not run in the rain. It will start and all, just sputter around. This is becoming a big hassle with hom getting stranded. I dont think its sucking water through the filter, its just like the intake on my truck and mine does fine in the rain. Any idea what might be causing this?

 

Maybe he needs not to drive when it rains. Intake might have a leak and its get on th maf

 

He needs to find a competent mechanic to trouble shot it. It could be fuel related, it could be electronic, or it could even be mechanical. It's just a guess with out proper diagnostics.

 

Get a dry charger for the k&n filter first. Should only be like $20-30. Put it on and clean the maf with maf cleaner.

Edit: Is it a cone filter or a drop in?