E320 Knocking!

[intruder]

I have a 1998 E320 wagon with 48,000 miles. It has a mild "knock" from the engine that's most evident when cruising or mild/moderate acceleration. (my wife drives it or I would have found it sooner) It's smooth as a bell at idle and during full acceleration. It's a little quieter during deceleration. Braking or turning have no effect. I added a bottle of Chevron Techron and changed fuel brands, but they had no apparent effect. I had the leveling system and drive-train checked at the dealer and it's fine.

I'm taking it into the dealer next thursday but, what else should I try or look for to help the mechanic diagnose this?

It almost sounds like it's not running on all 6 pistons or only 5 plugs (or would that be 10 or 11 of 12 plugs since it has 2 plugs per cylinder?) or like the dull popping noise of some inorrect valve overlap (but only on one cylinder.

Any suggestions would help>

Intruder

[Edited by intruder on 06-24-2001 at 02:22 PM]

[Southern]

Make sure that your wife fills the tank with premium gas (93 Octane). The 98 E320 requires premium gas due to the high compression engine. If lower octane fuel is used then "pinging" may result, in this case a bottle of octane boost may help.