I have a 1990 260e. From a cold start there is a noise which seems to be from the top end for 2 or 3 seconds during which time it misfires. In about 1 0f 10 cold starts a much lighter tapping occurs which stops suddenly after about 15 seconds. I use 10/40 oil which is changed regularly.

 

sounds like a the fan belt, idler pulley on the mercedes belt or a failing timing belt tensioner. try to check on these things. if you still can't find the prob, bring it to a shop to have it checked. hood luck.

 

Thanks for your help, I'll check those items out.

 

glad to be of help man by the way I am also using 10/40 - semi synthetic but I will try quantum silver also, I heard its cheaper LOL