Light "Clatter" and Intermittent Slight Bumpiness in Idle
 

Regarding the 2000 E430 4MATIC I recently purchased (119,000 miles), I noticed there is a very slight bumpiness from time to time at idle just above 500 rpm (the normal idle after warmed up). This is why I contemplate changing the plugs (or having them changed). This is intermittent, meaning it does not happen very frequently at all, and is more of a skipping or missing, i.e., impression is a misfiring from time to time. And, it is very, very subtle, not rough or dramatic. I am perhaps being overly sensitized by this as the :bowrofl:300E 4MATIC (1992 with 253,000 miles and still running) I have rarely if ever had a rough idle.

There is also a light "clatter" I can almost say it is the right front cylinder because if I put my ear close to the engine this is where it is coming from. I had failing or sticky lifters in the http://mbworld.org/forums/images/smilies/bowdown.gif 300E 4MATIC but the clatter on cold mornings (was actually a different sound) would go away after the 3-5 minute warm up period I am accustomed to before putting the car into gear.

I also believe this clatter tracks the rpm's such that when you rev it or accelerate the rythym (speed of the clatter) increases proportionally. I put two tanks of premium fuel through it so far and on last fill up treated it with a pint of Sea Foam (which I never ever did in the http://mbworld.org/forums/images/smilies/bowdown.gif300E by the way), because the guy I bought the 2000 E430 4MATIC from put regular gas in it for the 600 or 700 miles he drove it http://mbworld.org/forums/images/smilies/slap.gif.

He said physics say its the same thing to put 87 or 93 http://mbworld.org/forums/images/smilies/crazy.gif. I said http://mbworld.org/forums/images/smilies/bs.gif.

Anyway, to avoid any major engine problems, if the Sea Foam treatment and the premium gas does not blow out the stickiness / clattering sound, what are my options to have this "diagnosed" without being fleeced? http://mbworld.org/forums/images/smilies/nixweiss.gif Or is there any other self-help I can engage in without hurting myself?http://mbworld.org/forums/images/smilies/confused.gif

My ultimate plan is to bring it to a dealer and have them perform the full $208 pre-sale inspection as if I am going to buy a new one from them http://mbworld.org/forums/images/smilies/thumbsup.gif to make them tell me everything it needs, and then take it to my German mechanic and see what he says about it and start fixing anything major.http://mbworld.org/forums/images/smilies/biggrin.gif

Any thoughts or ideas. Thanks, CJ