I have a 96 blazer, and can't figure this out. It runs rough and is hard starting when it's wet out, but otherwise runs decently. I recently purchased the ac delco double platinum plugs and threw them in, and couldn't start it. I pulled them back out and they were wet. Blew out each cylinder with compressed air and reinstalled a few times same thing. I felt like I was banging my head against a wall.

Today I grabbed my spark plug sand blaster and cleaned up the old mix of plugs. 4 ngk, an autolite, and a ac delco rapidfire behind the steering rod. It started right away but runs rough under load (brake stand in garage) no codes set.

Any ideas?

 

How are the wires, cap, & rotor? Plugs are just one part of a proper tune up.

 

Cap and rotor is fine, wires were new a year ago.

Just ran it again after replacing the drivers side plugs, then replaced the passenger side and ran again. fuel pressure is at a steady 55 lbs when running.

The old plugs were filthy after a few minutes. black deposits.

 

Define "fine"? How old are the cap & rotor? What brand are they?

All of your symptoms seem to point to an ignition system problem.

These trucks really do seem to prefer AC Delco ignition components (cap, rotor, & plugs specifically).

 

Cap and rotor look brand new. No tracking, cracks, corrosion, etc. It's raining now so we'll see how she does in the morning.

 

I have never experienced the AC/Delco "like" for any of my GM vehicles,especially my jimmys! Running Bosch plats now 30K+ and NAPA/Echlin wires,cap & rotor-no issues! I do find that if one does not use dialetric grease at all connections the usual force needed to remove the wires will result in a fail even in top quality wires! Hmmm,but I DO notice that all my 4.3s prefer Valvoline oil & Purolator Golds...