I'm posting this again because I only got one response and it didn't really apply to my problem, so here goes...

My '86 300E with 120k miles pings noticeably on moderate to hard acceleration. Sounds like somebody's under the hood shaking a coffee can full of rocks! I've never put anything other than premium fuel in it (91 octane So. Cal. gas). I replaced the plugs, rotor, cap and complete ignition wire set recently, and when the plugs were out, they all had a nice medium tan color. None of them appeared to have any significant carbon buildup on them. I looked into a couple of the plug holes with a small penlight and there was just a normal light buildup of carbon on the piston crowns, so I'm at a loss. I do know that the valve guide seals were replaced about 30k mi. ago and currently oil consumption in very low, about 1/2 qt in 3k mi.

Is there any kind of knock sensor in this system that should adjust the timing when it pings?

Is there any manual timing adjustment that needs to be done?

As the cam chain wears, does the distributor timing advance or retard? As far as I know, the cam chain has never been replaced.

Can a worn out O2 sensor cause this? (btw, what triggers the o2 sensor light on the dash? Mine hasn't come on yet, but I'm just curious)

An old trick we used to use to remove carbon deposits involved introducing a fine mist of water into the intake tract. The sudden heating and expansion of the water into steam in the combustion chamber would blow off any excess carbon buildup. Could these carbon particle cause any problem with the catalytic converter?

Thanks for any help

Gary