I Cured A Random Misfire Problem-3800 V6

[GTPsurvivor]

Solution for me. Installed new premium AC Delco wires, put heat shields back on, no misses yet. Still running with disconnected solenoid. But I can accelerate again! 

[Schurkey]

On 4/12/2021 at 5:49 PM, GTPsurvivor said:

Solution for me. Installed new premium AC Delco wires, put heat shields back on, no misses yet. Still running with disconnected solenoid. But I can accelerate again! 

^^^WINNER.

The problem is NOT the heat shields.  It's faulty plug wires.  GM made a bazillion of those engines, and they were guaranteed to meet emissions regulations (i.e., no misfires that produce high HC and kill the catalyst) for 50K miles.)  The heat shields were designed-into that system.  Yes, they'd provide a ground path if the plug boot were faulty.  Removing the heat shields does not make the plug boot less faulty, it just removes an easy ground-path for the spark.

[Jim_rockford_007]

These came out of My Lumina that was having a bad stumble after the Engine swap. front 3 

[Schurkey]

Remember, thousands of years ago, when spark plug porcelains had "flashover ribs" to reduce that sort of problem?  Now, plugs are smooth-sided.  You found out the hard way what happens next.

I guess the plug engineers managed to shave off half-a-penny by producing plugs with no ribs.  Thank God for progress!

 

Another reason that dielectric silicone grease is essential.

Edited April 29, 2021 by Schurkey

[Chrisolds]

I had a random misfire under load for almost a year and went through so many good plug wire brands and plugs. It was miserable for me! Then once I worked on it in the dark bc I had to and I could actually see the blue spark arcing from the heat shield to the engine, it was jumping all over the place on 2 out of 3 of my front plugs. I just happened to catch it because it was so dark out. I took them off installed new plugs again just to be new and a brand new MSD wire set and I have never had an issue again. So yes trash the heat shields. I think the spring type thing inside the shield is what draws current from plug and then it just finds the least way of resistance to block causing the misfire. Can happen on any vehicle that use heat shields. 

[Schurkey]

17 hours ago, Chrisolds said:

I had a random misfire under load for almost a year and went through so many good plug wire brands and plugs. It was miserable for me! Then once I worked on it in the dark bc I had to and I could actually see the blue spark arcing from the heat shield to the engine, it was jumping all over the place on 2 out of 3 of my front plugs. I just happened to catch it because it was so dark out. I took them off installed new plugs again just to be new and a brand new MSD wire set and I have never had an issue again. So yes trash the heat shields. I think the spring type thing inside the shield is what draws current from plug and then it just finds the least way of resistance to block causing the misfire. Can happen on any vehicle that use heat shields. 

 

On 4/13/2021 at 8:06 PM, Schurkey said:

The problem is NOT the heat shields.  It's faulty plug wires.  GM made a bazillion of those engines, and they were guaranteed to meet emissions regulations (i.e., no misfires that produce high HC and kill the catalyst) for 50K miles.)  The heat shields were designed-into that system.  Yes, they'd provide a ground path if the plug boot were faulty.  Removing the heat shields does not make the plug boot less faulty, it just removes an easy ground-path for the spark.

It's not the heat shields that are the problem.