Rough Idle after heavy rain fall?

[zerodevil]

Hello gents/ladies,

I have a bit of an odd one here. Truck normally runs and drives excellently. but after it has been sitting all night with rain fall, the truck runs extreamly rough with an obvious miss on one or more cylinders. Once the truck reaches its designed operating temperature the idle smooths out and it runs/idles smooth as silk. I get no CEL and no codes can be pulled from the vehicle..Anybody have any ideas?


the truck does have some mods
MSD ignition coils,
K&N CAI
Magnaflow catback exhaust
JBL headers
BBK 78mm TB+Plenum
Professional products intake manifold.
93 Octane tune via henson performance.

 

[Everdream]

Check and make sure you aren't getting water on the aftermarket ign stuff, I didn't look at what you have, but one of my older trucks used to have an after market "box" that would run to the coil pack, than to the plugs and that would get water in it from where the moron before me mounted it (front core support), so once the engine heated up the water would dry up and good running truck........

 

[zerodevil]

i checked the coils for water, they were all dry, the spark plug holes were dry, and the resistances for the COPs are all the same, so no apparent failure on that end.. its not running in high rpm like it should though, its almost like the computer thinks the engine is warm and is leaning out the mixture to much?

 

[Everdream]

Strange, Have you done the typical MAF and IAC Cleaning? You may be able to hook up a scanner to it and look for fuel trims and see if you are indeed rich or lean.