Recently I have noticed an ocasional idle problem on my 1990 240. The problem only occurs after I accelerate hard or drive on the interstate. (above 55mph)I checked the codes and found that a code 3 1 1 was stored after each idle incident.(I cleared the codes after each test) My shop manual stated that this is "vehicle speed signal missing". I then replaced the speed sensor in the rear end cover. No Change in condition,still idle's fast at times as before and I'm still getting code 3 1 1. The manual stated that the adustment for the speed sensor is 3 thousands . Is this correct? The sensor I removed was the original and had one shim behind it but there seemed to be more than 3 thousands clearance on both the old and the new sensor. Thanks in advance for any help! David