Engine very little power when humid

[C350amg]

When I purchased this RV (our first) 1 month ago (it's a Triple E 1998 on P30 7.4L) I took it to a GM truck dealership for a complete overhaul. Suspension, direction, engine (belt, plugs wires,), all oils and a bunch of other things were all changed.

Engine runs very smoothly except one morning, it started perfectly but when but into drive you could feel the lack of power on some cylinders missing. It took about 1/2 mile running it and it got away. Next day everything was fine.

I left it park for one week where it ran pretty much everyday and when I took out again same problem. And again ran it with no power for 1/2 mile and it went away.

To me it looks like wet sparkplug wires but the thing is that they are brand new (less than 30 days old). It's either that or a pool of water is forming where wire pass creating some type of short circuit.

Ideas ??

[Geocritter]

My Dad had that problem years ago with a car. Upon inspection I found that moisture was condensing inside his distributer cap. I hosed out the cap with WD-40 and it was good to go. He lived in humid Ft Lauderdale FL at the time which may explain the condensation he was getting.
Steve
PS It's not such a problem these days, but in days past when you'd go through a large puddle at speed it would often make your engine conk out due to water (steam) getting into your distributer. I used to keep a spray can of WD-40 in the car just for those situations.

[Effy]

I have heard that on some of the older air filter units they can collapse when they get moist thus choking everything.