Explained in my last post that my DI cassette failed on my way to the garage to have a CV joint replaced. Managed to get it to the garage, misfiring heavily, and they diagnosed the DI cassette, which I had them change out. Since many on this group have indicated a faulty spark plug could cause a DI failure, I decided to look into it.
I have only had the '94GM900SE Turbo for about 20K of its 150K/miles (250k km) but I have fairly complete records for it. Checking back through the records it appears the last time the plugs were changed was
7 years and 103000 miles ago! Time to get something done about it! So I ordered-in 4 BCPR7ES, gapped them to 1.1mm (they come gapped to 1mm, so pretty close) and replaced them, torqued to 28nm.The No 4 plug was actually a bit loose in its socket. Loose enough that I wonder if how it could actually seal properly. Other than this, I am just astonished to see what good shape the old plugs are in. They all have very light, brownish-tan deposits, and the electrodes are in good shape. Nothing distinguishable about No4, so it must have been just tight enough to do the job. There is a small cusp of erosion on the firing side (underside)of each curved electrode, which has increased the gap to about 1.3mm, but that?s nothing. I?d say they are in near perfect condition, which is a bit surprising for plugs that have 100k miles on them. I take this to be an indication of a motor in overall fine shape for its 156k/miles.