- Acceleration was not smooth, check engine light came on. Symptoms disappeared on restart of engine.
- During hill climbs, acceleration decreased dramatically, symptoms disappeared for time after engine restart. Each successive restart resulted in a shorter and shorter time before symptoms represented. Check engine light came on after multiple restarts.
- OBD II P0121: Throttle/Pedal Position Sensor/Switch ‘A’ Circuit Range/Performance Problem
- OBDII P0299: Engine Turbo-Supercharger Boost
Problem: The turbo resonator is made of plastic and the seam failed. This is a known failure point according to multiple forums. Mercedes has been through three revisions of this part in plastic and it keeps failing.
Solution: Previous owner had the turbo resonator replaced once by Mercedes dealer and they put in another plastic version. Previous owner decided to purchase an all aluminium replacement part and it transferred to us when we purchased Abby. Repair was simple enough, complicated by rain and being parked in an emergency pull-off area along I-76W. Requires low clearance 1/4″ socket (which we did not have). We limped into Somerset, PA with an escort by a Herring Motor Company tow truck (fortuitously helping an automobile with issues in our emergency pull off), to purchase a $9 socket wrench to properly execute the repair. Dave performed all mechanical repairs. Jess served as chief child and dog wrangler and did not bake cookies while waiting for the repairs to be completed.
- Still have the plastic turbo resonator in? Just order the all metal version and replace it before it fails on the road. Repairs are always easier on a nice day, parked in your driveway/workshop, without traffic flying by at 70+ mph. An inexpensive repair (if you do it yourself, several hundred at a dealership) that will save you time and headache on the road.
- This is a repair you can do yourself if you are comfortable doing basic maintenance work on your vehicle. It is two hose clamps. That is it. The working space is tight, which adds to the challenge.
- Have your outdoor rug easily accessible. It doubles well as a work pad
- The metal part does whistle. So don’t panic. It may be noisier, but it won’t leave you stranded on the side of the road.