I drive a 1985 500 SEL...and recently it has been acting a little funky when I accelerate. From 0-20 mph it acts a bit shakey and feels like its popping...But once I get it out of 20mph it acts normal when I accelerate more. Though I don't seem to be able to reach 85 mph.

If anyone has any thoughts or knows what it is, please let me know. Cheers.

 

does it idle rough ? sounds like u have a misfire caused by vacc leak in the intake manifold. which would cause a rough idle. idle the car with air cleaner off use brake cleaner spray around the fuel injectors in short burst and around all plastic hoses and rubber hoses if he idle increases or smooths out theres your leak and will require some resealing of intake manifold see other post i made to others with m116/m117 engine problems the repair pocedures are outlined