at idle occasionally, and even died a couple times-emgine temp doesnt seem to matter. All this after 2000 miles of flawless operation since I bought it - car has 156,000 on clock. I began to think it might be bad or lower-than-advertised octane fuel, or that I might have screwed it up by pressing down on accellerator once when just started. Seems to maybe have gotten better since last fillup. Any thoughts?