Folks PLEASE help me. I have a '96 Park Avenue Ultra with the 3800 Supercharged engine. Just turned 100,000.

:banghead: Spark Plug #4 keeps CRACKING and then misfiring. The crack is in the porcelain area. It always looks like electrical arc through. I've been through 4 plugs in the last 100 miles. The DTC Code that comes up is P0304 - Misfire Cyl #4.

I've put in new plugs.
Replaced the Coil Pack (for cyl #1 & #4)
Put in high quality Fuel Injector cleaner.

The heat shields are all there.

Has anyone ever heard of this? Three folks told me it MUST be the coil pack - but no change.

Then someone suggested maybe an injector is staying open and flooding the cyl causing the problem.

I'm lost and sure could use some help.

Thanks!!!

Dave

have you ever though of changing the spark plug wires? # 4 could be faulty.

Replace the ignition wire set. When you do that make sure you put a new plug at # 4 at the same time. The old plug has carbon tracking on it and the problem will start all over again. Good Luck.

Tman is right GM had a problem with plugs cracking back then. The problem is heat build-up in the wire which overheats the plug and it carcks. Replace the wires and plugs and the problem will be gone.

Yahoo!!! That did it. :grinno:

I put new wires in, have driven it for over 200 miles - and wa la!!! no more missing or cracked plugs!!! MANY, MANY thanks to both who recommended I change the plugs!

I did measure Plug wire #4 and it read 175,000 ohms, most of the others read about 145,000 - 150,000 ohms. Sure didn't take much.

Thanks again all!

Dave