You said that it started when driving in a heavy rain storm. There may be an additional solution to this besides the temp II, plug wires having small cracks in them and hold moisture/water. WD40 is your friend, spray the engine wires down really good and see if it cures a rough idle. BTW, 87 Westy's are the best year!
good video tip... having the same issue on my 87. also, my tach can be iffy so I'll also check those wires.
Thank you, thank you, thank you. Fixed my van after watching this
You said that it started when driving in a heavy rain storm. There may be an additional solution to this besides the temp II, plug wires having small cracks in them and hold moisture/water. WD40 is your friend, spray the engine wires down really good and see if it cures a rough idle. BTW, 87 Westy's are the best year!