98 Jimmy bogging down

I'm having a very unsual problem with my 1998 GMC Jimmy (4.3 L Vortec) and I cannot figure it out. The vehicle was running fine and then I went througha puddle that was deeper than I thought. After coming out of the puddle, in which the underside of the vehicle was submerged the Jimmy ran fine for about 15-20 min and then began bogging. In normal running it will idle at around 600-800 rpm however as it began doing this the rpms will drop below 400 and then will die. If I wait a moment sometimes it will crank but the moment I put it in gear it will bogdown and die OR as I apply pressure to the accelerator it will jump forward a few times and then die. I initially thought I had water in something so I let it sit for more than 24 hours before starting it again. It ran fine for about 15 mins and then it began doing the same jumping forward/bogging down thing again. I'm really confused here.

I checked the fuel pump and it appears to be fine as is the fuel filter. The engine is new, full engine replacement about 2 months ago so all new plugs, wires, distributor cap, valves, tranny, rear end, etc, etc, etc. I'm wondering if I have water in a wire somewhere but just not sure where to start looking. I'm not the best mechanic in the world but I'm passable with good direction. My brother is the mechanic but he won't be able to look at it for awhile and frankly he's done enough for me with this thing. Anything that anyone can offer would help! Thanks

Well how deep was that puddle?

Any check engine lights on?
Any codes?
Have you looked inside the dist cap for water?

Was the water over the fuel tank vent?

The puddle wasn't too deep but came to about the bottom or running boards. Definately was not even close to being up to the fuel tank vent. With the up spray definately got the engine damp but not soaked.

No codes at all when I had it put on the scanner. No lights on the dash board although the low fuel light came on briefly after it happened but went out fairly quickly.

I noticed that the fuel gauge has fluctuated quite a bit after this. Intially thought that maybe got some moisture in the fuel lines so filled up and added gas line antifreeze to no avail. The truck has a locking gas cap which I am not a fan of as it doesn't seem to have the best seal. Any chance I do have a little bit of moisture in the fuel tank/lines?

I'll take a look at the distributor cap and see if there is moisture in there. I'm thinking its a damp wire issue somewhere as it was running fine prior to the puddle. Any other ideas on which wires I should be looking at? Thanks in advance for the help.

The puddle wasn't too deep but came to about the bottom or running boards. Definately was not even close to being up to the fuel tank vent. With the up spray definately got the engine damp but not soaked.

No codes at all when I had it put on the scanner. No lights on the dash board although the low fuel light came on briefly after it happened but went out fairly quickly.

I noticed that the fuel gauge has fluctuated quite a bit after this. Intially thought that maybe got some moisture in the fuel lines so filled up and added gas line antifreeze to no avail. The truck has a locking gas cap which I am not a fan of as it doesn't seem to have the best seal. Any chance I do have a little bit of moisture in the fuel tank/lines?

I'll take a look at the distributor cap and see if there is moisture in there. I'm thinking its a damp wire issue somewhere as it was running fine prior to the puddle. Any other ideas on which wires I should be looking at? Thanks in advance for the help.
Yes and no on water in tank.
Water up to running boards can roll up to tank vent and also can get blown back on and in dist cap and I have saw the water get into air filter.
Check inside dist cap real good.
Check for good hot spark to all plugs.
Check fuel filter for water in it and also check fuel pressure.

Thanks I'll take a look at all of that and post what I find.

I was tinkering with the truck a little tonight and noted a few things that might help to narrow the problem.

The truck fires right away with no hesitation and will run just fine up until the temp gauge reaches about the halfway mark and then the issues start. The truck will bog down/jump forward ONLY when in drive. I can rev the engine way up in neutral and park and it will drop to about 400 rpms but will continue running. If I try the same thing with the truck in drive it barely begins to rev before it dies. If I let everything cool off and the temp gauge to drop then everything starts over again like nothing happened.

I also noticed that when it begins to do the bogging/jumping forward thing that there is a small popping noise from the exhaust. Not a full blown backfire but a minor pop sound.

The air filter is bone dry and the dist appears to be ok, but I haven't run a full test on the spark wires or on the fuel system yet.

Does this sound like a fuel issue or is it spark issue? I'm also wondering if I have water in one of the injectors or something.

I can hear the fuel pump running when I turn the ignition on but don't start the car and it seems to sound fine.

One time when my Cat conv was going bad, my 3 cyl chevy sprint acted that way, ran fine at cooler temps, and like butt once it got warmer. would barely move once it got warm.
could always try tapping it to listen for chunks rattling in there. possible the cold water on hot exhaust did something to it

Something also tells me to look at your Egr and make sure no chunks are plugging it

I was tinkering with the truck a little tonight and noted a few things that might help to narrow the problem.

The truck fires right away with no hesitation and will run just fine up until the temp gauge reaches about the halfway mark and then the issues start. The truck will bog down/jump forward ONLY when in drive. I can rev the engine way up in neutral and park and it will drop to about 400 rpms but will continue running. If I try the same thing with the truck in drive it barely begins to rev before it dies. If I let everything cool off and the temp gauge to drop then everything starts over again like nothing happened.

I also noticed that when it begins to do the bogging/jumping forward thing that there is a small popping noise from the exhaust. Not a full blown backfire but a minor pop sound.

The air filter is bone dry and the dist appears to be ok, but I haven't run a full test on the spark wires or on the fuel system yet.

Does this sound like a fuel issue or is it spark issue? I'm also wondering if I have water in one of the injectors or something.

I can hear the fuel pump running when I turn the ignition on but don't start the car and it seems to sound fine.

Run the fuel pressure and spark test when it is acting up and watch and check for codes.