Need Help - Difficult Problem

I have a VERY frustrating problem with my 2004 Toyota Tacoma. Here is what's happening...

5-6 times over the last couple months, my truck will stop on me while driving, or won't start when I try to start it in the morning.

The common theme during this occurences is rain or very high humidity following rain.

The dealer seems very perplexed, because after the truck is towed in it usually starts fine and they throw their hands up. They did see the problem a couple of times, and while the truck wasn't starting, they said the computer wasn't responding to them (at least once)....they replaced the computer, but that didn't fix the problem.

When it won't start, everything sounds perfectly normal when I try to start it - I mean the starter seems fine and the truck seems to get extremely close to starting, but just won't fire up. A couple times, it started, ran for maybe 5 seconds, then stopped again. After that, it did not start again until the weather improved.

The truck runs great on normal dry days.

This seems like a ignition system problem, but I'm not sure? What are your thoughts?

Please ask me questions if you have any.

Cam position sensor and Crank position sensor can both cause what you describe. Also test the MAP and MAF sensors.

Thanks for answering Curtis...

would those sensors show signs of malfunction during rainy days?

This rain thing is the only consistent part about the whole situation.

They could. Theoretically any sensor can malfunction in the rain if its getting moisture in it. Another possibility is that a corroded connector or shorted wire is only getting shorted when its damp. My fuel gauge only works when its raining - the ground wire is corroded and the water completes the ground.

While it is messing up it should be rather easy to figure out what is wrong. You only need fuel, compression and ignition to make an engine run. Since it most likely isn't compression fuel and ignition are your most likely sources. If it has a malfunctioning sensor, cam or crank likely, the injectors and/or coil probably aren't even firing. But, anyway it should be somewhat easy to figure out while it is doing it.