2600i stumbling when humidity is high
 

My 2600I pickup is stumbling whenever the weather has been really humid or rainy the night before. It will start and high idle fine but as soon as the idle drops it will start missing on cylider 2 and 4. Thinking it was ignition related I replaced it ALL, distibutor cap/rotor, plugs/wires and coil with no change. When this occurs I have spark at these two cylinders and the exhaust smells of raw fuel. This stumbling will only last for maybe 5 minutes or so and the truck will run fine after that even in a pouring rain. If the weather is dry this truck never skips a beat. I have tested for water in the fuel and none is present. This is driving me nuts and can't be good on the engine. Any help would be GREATLY appreciated.

RE: 2600i stumbling when humidity is high
 

Im having a similar problem with the same truck, I also would appreicate some help.

RE: 2600i stumbling when humidity is high
 

If the ecm in your trucks have never been repaired, check this site. He repaired mine in 04. He knows what he is doing. Good luck.

http://www.avproecm.com/