GMC Repair: stutter and power loss during rain, bosch platinum, electrical harnesses

Question
Hi
  I have a 1995 GMC Sierra (K1500) Z71 (4wd) with the 5.7L engine. For some time now, I have been experiencing stuttering and power loss at higher speeds during rain--ONLY during rain. Particularly, when there is enough rain on the road that tires are throwing rain up at the underside of vehicles. I asked a local mechanic and he said my problem might be my plug wires, so I replaced them, though they did not appear dry or cracked; I have ensured that I used dielectric grease on the contacts.  This did not fix the problem.
  The stuttering generally happens above 55mph, and gets so bad that I have to drive in 3rd gear and feather the accelerator, otherwise power will start to drop and just keep dropping, usually followed by a sudden surge of power again.
  Have you seen this, and do you need more information to point me toward some courses of action on what to look for? I had initially thought it was either an electrical issue or that I was getting water sucked into the fuel line somewhere. 2 of my plugs (Bosch platinum standard) were also bubbled out at the ceramic end slightly (2 rear left cylinders {toward driver}, 5 & 7, I believe).

Any helpful directions to go in are appreciated.

Thanks
Steve


Answer
Personally I NEVER deviate from what the manufacturer suggests for replacement parts when replacement becomes necessary. I would instll the ORIGINAL type of spark plugs that is recommended by the manufacturer and your power loss is mos likely from the carnkshaft sensor getting wet and or one of the electrical harnesses down near the lower portion of the engine may be damaged and is getting water in the connection and or harnes assembly.


YES, I have seen this numerous times. Check ALL your electrical connections.

Are you the ORIGINAL OWNER or are you the SECOND or THIRD owner and do you know the past and current repair history of the vehicle ?.


autohlp