As some of you know from my last post, I got a P0300 misfire code and a P1811 transmission code and the car wouldn't move under WOT. I changed the plugs today and the problem is now gone. I put the NGK TR55'* in last April and they only had 18k miles on them. Is this the normal life span for copper plugs in an SC engine? Also, why did I get a transmission code from a misfiring engine? Thanks....



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Probably just 1 plug bad (maybe the third from the left?). That happened to me on a set of brand new AC'* not too long ago. By a stroke of luck the first plug I pulled and subbed was the bad one. Got lucky.

How many miles on those plugs? I notice the center posts look more worn than I would expect if the miles on them are low. Mine didn't look that bad on my '92 at 100k. Of course posted pictures can be deceiving.

They had 18,000 miles on them.

Test your wires and ignition packs. I believe the specs are in techinfo.

90,510 miles on them and still going strong.

AC Delco double platinum 41-921





The photos are the way they came out. I then cleaned them up a little bit with a wire brush before I re-gapped them and re-installed them.

Thanks for a post of a plug that is not found in the supercharged engine MAC

I'm surprised by the misfiring at that mileage although it is possible one cracked etc. As for the trans code, keep an eye on it. That may have been induced by the issues/misfiring.

I had 180,000 miles on a set that I took out and they were still working well. Just decided to replace the plugs and wires when I did the intake manifold job last year.