ok so thanks for reading. I just purchased an 1995 mercedes S420 with perfect interior everything works but heat and pass side seat adjustments. it has 163,000 miles on it and had to have been taken care of due to the condition of the vehicle. I have a horrible hesitation/bog/powerloss under acceleration and idle( not as bad at idle) for sure its some type of missfire. seems like fuel delivery. Someone told me it could be a bad vavle. Im in fere for my life... lol any back yard tricks anyone knows to lead me in the right direction to see if it is a vavle... Im not worken with a ton of money im hopen its an injector.... i have to get to the bottom of this thanks so much.

 

Check to see if the seat is plugged in.. if neither is working maybee someone unplugged the seat for some reason..

 

gearwrench, It sounds like your MAF sensor has failed (Mass air flow).

 

go have the fault code check, do not attempt to do guessing game as it will be costly by the end. do it the right way in diagnosing for the hesitation, could be a lot of factor and when you start replacing parts one at a time to play hit and miss you will end up with too much unnecessary expenses. Best is to take it to a trust worthy mechanic with real experience on 140 series.