My 88 420 with 149K has a slight "rock"
when I first turn it on: hot or cold start.
Its had this for a long time. MB dealer said I needed a valve job- that was 45k miles ago. Second MB dealer said it needed valve stem seals. That was done- car ran fine since. No more burning of oil.
The rock continues but diminishes slightly as the car is driven. Once in a while it will run perfectly smooth. Most of the time it has this "rock"- more obvious in neutral,
less in gear. 150K serivce has been done. Always dealer parts. Engine is smooth on acceleration and never misses, stalls, hesitates. Any suggestions?

Have you check your engine mounts... and also
1988 modle 420 SEL idle ca be raised 50 RPM
when transmission in gear ask a experince MB tech should know how to do it.

------------------
MB STARS Master Guild Technician,12 years MB tech
5 years independent shop owner

The other thing to add to Mb stars is the injection nozzles. Have them checked too.

------------------
Benzmac:
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM

Motor mounts were done as was engine shock absorber. Great suggestion on checking the injector nozzles. I am 2nd owner-car has 149k- should they be cleaned (what method & tools), checked (what would you be looking for) or just replaced? Thanks in advance.