I had the same problem with my Acura CL-S. It pinged like a mother and it was never fixed. Acura USA wouldn't take the car back, because they said that the knock sensor would retard the timing to take care of it, and I should just drive it and stop complaining. I eventually just took a loss on a 1 year old car and bought an Audi.

I had a similar pinging in my 4.8is, but fortunately, a bottle of techron has fixed my issue so far.

I know how you feel, LVR, it really sucks.

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Scott in Cincy
2008 X5 4.8 (wifey)
2009 AMG E63 (Daily Driver)
1997 Porsche 993 Turbo
1968 Mustang GT Fastback -- Resto Project
1969 Firebird 400 -- Resto Project (Trans Am Replica)
1996 Saturn SC2 -- LeMons Racecar!