I changed my spark plugs last week to NGK Platinums and I must say I was impressed with how smooth the engine was revving. However, at night, after about 4500rpm it started coughing, spluttering and running really rough.
I have had this problem in the past but it wasnt quite as bad and occurrences were few and far between, so I didnt think much of it. It was just strange how it only happened at night. At first I thought maybe it was running a bit lean, but thank god the problem was much simpler than that.
I remembered this thread and how rev210 had his plugs gapped to 0.70mm. I checked my new plugs and found that they were 1.1mm (which I was told is standard?). So I regapped them to 0.75mm. Bad idea! Sounded like the engine was running on 2 cylinders. I then regapped them to 0.85mm and all I can say is MY GOD! The car has never, never, EVER been this smooth all the way to the readline. The application of power is incredible, the engine sounds better, and I can feel a slight increase in performance.
I cannot recommend this more to anyone! If you've got copper plugs I'd gap them to 0.7-0.8 and if platinums 0.8-0.9. You wont believe the difference :uh-huh: . Now, more than ever, traction is my worst enemy.