Power Issues mostly when raining

[xredge]

OK gota weird one that is off an on. The issue now seems so far just to happen when raining but haven't been driving it when needing lights recently either. Been fighting with this off and on for over a year but don't drive it much but starting to mod it and want everything right first plus will help when pulling the trailer only had one issue with the trailer last year when pulling and was raining. Yesterday was pretty bad when driving it in the rain. It is a 94 K2500HD 5.7 with the 4l80e trans. What usually happens it starts out running great even spun the tires leaving the driveway yesterday (rain helps lol) but after 2 about 2 miles it started backfiring and losing power usually right around 2000rpms and shift points sometimes backing off and hitting the gas helps and a lot of times it backfires or surges once and then takes off with no more issues and sometimes it just bogs.

Items replaced so far: Battery, alternator wire (had short in it), coolant temp sensor, O2 sensor, Plugs, Wires, Dist cap, rotor, coil.
Have a new dist just have to put it in. Also checked ground wires from battery and goes to intake and fender like I believe it should. I did just find out looking at things that my body to frame ground is no longer connected (the one that is one the passengar side that connects to the body by the coolant lines into the body then down to frame, and when I went to grab it, it crumbled so going to order one from Summit tomorrow as I have to leave soon, wen to the local Oreileys when I was in town they had it listed but not sure if they could get it and was more than double the cost from Summit. Also which might help with this had some trailer wiring issues last year just reused the trailer harness but had to replace the brake switch and add another power connection to the brake controller was going to rewire it this year if needed it seemed the ground in the rear was connected to the frame but sometimes the left lights and blinkers would not work and at times effected the brakes. Usually runs great when dry, and after replacing the coil a couple of weeks ago it seemed all fixed until yesterday with the rain.

Any ideas? And any other grounds should I look for besides the frame to body ground.

 

[89rcsb]

I know they're new wires, but have you run the thing and looked for arcing? Best to do that after dark. Take a spray bottle full of water and spray it on the ignition wires, that'll help show arcing.

If it only runs bad in the rain, that's almost always an ignition voltage leak. Of course, the new ground strap won't hurt anything. But, my truck has been missing the frame to body ground for as long as I've owned it and I don't have any running quality problems at all.

 

[xredge]

Nope haven't tried that but will, but it used it do it sometimes also when not raining. But from the limited driving it does get, it seems that it acts up the worse when its raining or when you turn the headlights on, and thinking about it while typing this I'm not sure i flight rain effected it that much I think it got worse with the heavier down pours with the darker skies and have to turn the lights on. And yes had the alt checked out and by going by the factory gauge it stays where it should just drops a little bit.
The reason for replacing the dizzy is because when I replaced the cap it was rusty inside so I cleaned it up the best I could with it in place, but just figured when gong through things to replace it but replacing the cap should have taken care of a cracked cap.

That is what I also thought about the ground, runs great otherwise. But with the trailer lights acting up sometimes and then when turning headlights just sort of wierd and it is a hit or miss thing just the other day it acted real bad prompting the post.