Well I hate to admit it but I was wrong about some types of sparkplugs. When I bought my 240 the first thing I did was tune it up, installing new wires, cap, rotor, and PLATINUM tip sparkplugs. It ran ok when I bought it and ran better after the tune up. Still it seemed to have more of a swing in idle speed that I would expect and seemed to be weak on acceleration. I wrote off the lack of hp to the normal volvo engine performance.

In the past I would have said all sparkplugs are the same and only went with the Platinums for longevity. The other day the old girl seemed a bit sluggish after only 30,000 on the tune up. So, I decided to change the plugs. This time I decided I would go with NGK copper plugs instead of Platinums. I pulled the plugs and they were all clean, normal color, and normal gap. In short, all in great condition. After putting in the copper plugs BOY!, was I surprised! The engine settled down to a very smooth idle, much more so that when I first tuned the engine. It accels better now, more power, in short the engine is just simply running better on the copper tips than the platinums.

I still cannot explain why this is so, but for volvo engines I will no longer use platinum tip plugs.