Driving home from the airport last Monday I had to downshift to pass an idiot who decided to pull up next to me and sit there. I slowed down - he slowed down. I sped up - he sped up. Once I was at 75 he dropped back. In third gear this puts me close to 5,000 RPM and my car started to misfire like crazy. After I got over so I could exit I downshifted again and at 3,000 RPM started getting the misfires again. I figured it was the spark plugs since I know the BKR7Es erode quickly but I didn't expect them to go out at 9,000 miles.
Fast forward to this evening after purchasing and gapping a replacement set. I pulled the plugs out and they had eroded from 0.025" to 0.030", which shouldn't generate spark blowout. I did notice that one of my coils was caught so I regapped the plugs to 0.025" and straightened out the coil. Reassembled and took my car for a 6,000 RPM spin. Smooth as silk.
I suspect I had a coil that wasn't seated properly and the extra gap combined with a misaligned coil was the cause of the misfires. What's odd is these were the same plugs I put in prior to my 4,600 mile road trip in May and I know I had the engine above 3K on occasion but I seriously doubt it was ever above 5K except when coasting in DFCO across the Molly Stark Trail in southern Vermont. Also, for those of you who remember my broken dipstick based oil leak I didn't have any oil or oil residue under the Ecotec cover. I got lucky on that one.
Oh - it appears, based on looking at brand new plugs vs. the plugs in my car that I have another 8-9,000 miles on them.
One thing I didn't test yesterday was WOT to the red-line at normal operating temps. I did so today - hit the 6,500 RPM governor in 2nd gear. Smooth all the way to the red-line. I really think I missed one of the coils when I put the plugs in and until the plug wore down 0.003" it didn't matter.
Also, when I unscrewed the ignition rail it literally popped up and came right out.