95 350 shuts off after rain
 

Hello, I have a 95 Silverado 350 with 195k that idles rough and eventually dies if it is exposed to any kind of humidity. (Not during a thunderstorm but a day after if its humid) It starts fine and idles for 15 min before it starts surging and then dies. During acceleration it sputters and dies when I let off the throttle. After it "dries out" it runs like a champ. I replaced the intake manifold gasket, distributor, cap, rotor, wires, almost every sensor on the truck, fuel filter, rebuilt TBI, set the timing ect. to no avail. Fuel injectors are spraying consistently. also checked the fuel pump pressure while it was surging and it was normal. Also no cat on the truck. The only code I have is for the egr valve (it's been on forever and always ran fine) the egr valve pulls a vacuum when tested. At this point I think its electrical? Any input would be appreciated.

what i would do is try spraying the sensor connectors with wd-40. this should displace any moisture and "fix" the issue. another thing to check out is poor grounds, i would take them off and clean them and retighten and see where that goes. i would prob do that before spraying wd-40

Thanks for the help, I sprayed and applied dielectric grease on all my connections when I replaced the sensors. I double checked my grounds and they are good. Also when the truck surges and is about to die none of the dash lights or headlights flicker like they would if a poor connection was present.

Try spraying the distributor; look for condensation under/in the cap

Thanks for the input, I had the distributor replaced a few weeks ago with a new gasket and all. No moisture there. I have an idea what the problem is. From my understanding the egr valve sucks fresh air mixed with exhaust from the manifold and then pumps it back into the TBI via egr sensor. I replaced my exhaust manifold with long tube headers 2 years ago. Is it possible that the headers aren't allowing the proper exhaust:air ratio to be pulled into the TBI? Now instead of a mix of exhaust and air it's now just air getting pulled into TBI, and when the humidity levels are high, moisture is getting into the injectors and screwing up my air:fuel ratio?

Regardless I am going to try and plug off the egr valve and the vacuum lines attached to it.