multiple misc. cyl. misfire

[jims59vette]

I am a newbie to this forum. I have a 96' 1500 sierra ec w/5.7L , auto. I've had it for about 5 yrs and fixed it up for my retirement wheels. The only problem left is a mutiple misc. cyl. misfire, code P300. I replaced the usual suspects, Distributor cap and rotor, plugs and wires. coil and driver. I just keep clearing the code (about once a month). I suspect either moisture in the distributor or something electrical ( I can hear some low level static in the radio). A few weeks ago it was super humid and drissled a couple of days straight and the windows were all fogged up.First time ever that it didn't start right up, it turned over and over coughed and sputtered anf finally started and was smooth idling after letting it warm up. Waited a couple of hours and had a little trouble starting but nothing like when it sat idle in that slop for a couple of days. The warm front moved through, next day things dried out and it started right up as usual. I read on another forum that GMC distributors have a moisture problem. I'd appreciate to hear about similar problems and a possile fix. Thanks.

 

[jims59vette]

I am replying to my own thread, in hopes it will be helpful to someone with similar problems.I found extreme oxidation on the distributer cap and rotor contacts. I took my dremel with wire brush attatchment and cleaned the cap posts and rotor contact. It now starts and runs strong with no new codes as of yet. P.S. ,I have ordered a new Delco distributer cap and rotor.