I have had an ever-so-slight miss at idle when the 'burb is warm and in drive. I started out by changing the air filter, cleaning out the throttle body (which was carbon-fouled pretty bad) and replaced the throttle body base seal for good measure...this was all done about 3 months ago. I also ran some fuel injector cleaner through the gas at that time.

My truck odometer reads around 205K. The engine was replaced with a used one about 80K miles ago, and it had about 80K on the engine...at least that's what the PO told me when I purchased it in October.

Fast forward to today. I found a good deal on some Platinum AC Delco plugs at O'Reilly's (about $4/ea). The weather was good, so I knocked out the spark plug change. The suckers were on real tight... I had to use a breaker bar to break the torque on them. I started on no. 8 and worked my forward then went to the others side and started on no. 7 and worked my forward.

I found it odd that the gap is so large, set at .060.

Here are the pics of the plugs that I took just after removal. In order from 8,6,4,2 I'll add 7,5,3,1 in a second post.

At first, I feared I might have a small head gasket leak...but I think these plugs may have been original factory and were just that bad. I'll check the burn on one or two of them in a few weeks to see if I still have that white buildup on the plug...hopefully not, as I feel that may be a head gasket leak or cracked block/head causing antifreeze to leak into the cylinder...which would explain a slight miss.

After I changed the plugs, the miss is still there, and at times a little more pronounced than before. What I find odd is that the tach sits solid at 600 RPM. Even though it feels like the RPM may have dropped, the tach shows it solid.

 

As promised:

 

i just installed new plugs on the 95 5.7 I just bought. 6 plugs were at .056, one was at .045, and one was at 0.69. Fixed that miss...

 

I gapped all the new plugs to 0.60 and still have the miss.