P0301 – hesitation during rain - 2001

Thanks to all the members for their help

After having a permanent CEL for about a year I had the codes checked and came up with P171/174, P1401 and P0301. Using this forum I replaced the DPFE sensor and did the 171/174 fix, including cleaning the very dirty egr ports, and had the codes cleared. This eliminated the rough running at idle and the van ran great for about 2 weeks.

This past Friday, it rained heavily and the car had no power in mid rpm’s under acceleration and the CEL would flash. It has done this before, usually during or just after rain – about 3-4 times / year. I assumed the other fixes would take care of this. It seemed worse this time and took an unusually long time after the weather cleared for the problem to go away and the CEL has come on permanently. I had the codes read last night and only code P0301 came up.

The van is currently running fine. It is a 2001 w/ 95K miles. I had the plugs and wires changed at around 60K when a similar feeling problem was occurring in dry weather. My current plan is to run a fuel cleaner through the engine and when I have time switch the wire to see if this is the problem and apply dielectric grease to wires and connectors to try and seal out the rain

Any other ideas, items I should check? Any ideas why this seems only correlate with the rain? This problem is quite annoying!

The best fuel system cleaner that I have found is also one of the least expensive.... Berryman's B-12 Chemtool.

The miss during moist weather may be a electrical issue...as those get worse in moist conditions.
Spark plug wires and Coil pack are 2 leading suspects in that.
Sometimes you can see the arcing by looking under the hood with the engine running in the dark.....but cylinder #1 is on the back, driver's side of the motor, so it would be tough to see.