i'm not sure what to think of this problem. if i drive my 90 chevy pickup through water and get the undercarriage wet, the engine will surge to the point of quitting. the engine always starts after the truck quits, but it will still surge until it is dry. if i look at my o2 sensor readings when it's surging, it will go from 280mV to 1400mV. normally it should be about 480mV. i've made the obvious repairs: replaced a cracked manifold, replaced o2 sensor, replaced o2 sensor wiring, new distributor cap, spark plug wires, and the engine was also recently replaced (the problem existed before the new engine, as well). i have no clue what else i can do to fix it. could it be the ECM is bad? i don't know, please help!!!

 

one quick thing to try is to spray aater proof sylicon on the cap wires and all the electrical and see if you can seal the wires that may help a bit.