1987 base, stock L98 except for exhaust mods from the manifolds back... Yesterday I changed plugs, reason was I did intake gaskets 1500 miles ago and wanted to replace the plugs too but just got around to having time to do it. I removed a set of NGK standard plugs that had 3000 miles on them, and put in a set of AC Delco Rapid fire #5. The plugs were pre gapped at 45, and the gap per my sticker for the car is 35. After debating and some googling, I left them at 45.
After getting them in, when I tried to start the car, it would spin, hit and run for maybe 1-2 seconds. Tried this several times, same result. Checked all my wires, and sensor connections, tried again, same result.
I then gave it a little pedal and started it, it would run but only if I held it around 1000-1200 RPM... wouldn't idle, if i let of the pedal it would die. It did this a couple times so I went over everything under the hood again. When I couldn't find any problem, I started it again, held it at 1000-1200 RPM for about 2 minutes, when I let off this time it settled down and idled at the 700 RPM mark. Each time I started it after that it cranked and idled fine. Drove it about 10 miles, ran great, pulled like it always has. I let it cool all the way down last night and tried it this morning, started right up and idled fine.
Now the question is, what could have happened? Anyone else have this with the Rapid fires? With the old plugs, NGK, that I put in 3000K ago, it started right up no problem. Any thoughts or opinions would be great.