I have a 2000 Escalade with 169,000 miles on it. Runs great until it rains. Then I have problems with it starting. It turns over, starts but dies. After letting it sit for 2-3 hours, it starts right up and I have no problems with it for a while. This doesn't happen everytime it rains, but that's one common factor. I've had the fuel pump and assembly replaced, recent tune up. What could be causing this.

Any trouble codes? First step is to find them.

Running bad in the rain is the classic symptom of failing spark plug wires. I don't know if the 2000 Escalade even has plug wires anymore. Checking for codes should still be the first step though.

Any codes?

It has them, but they are short. The trucks have the (supposedly) more robust coils.

I would look at the CTS/IAT. With a datalogger, when cold, they should match within a couple degrees of each other.

You can take the connectors of each and put in a resistor of the same value in each, one that matches room temp (there is a chart I know I have posted before, can be found easily on the net) and see if that clears it up.