ikb435

Help! My 1984 500SEL (US Spec), has a serious engine vibration at idle up to around 2000 rpm.. it also stalled a few times on initial start up then proceeded to get worse. My mechanic (not a Merc mechanic I live in the middle of nowhere) said it was the wrong kind of spark plugs and changed them and initially it worked, but he started it up again and the problem has persisted. He thinks it's the injector pump... (Do they have an 'injector pump' per se?). Any advice would be appreciated.

cylaptor

let's start first, does the car start quickly or does it take a long time? on the first ball it acts as its an air flow sensor

ygmn

should have ODB1 anyone check to see if it threw a code?

ikb435

It starts on the first try.

ikb435

It starts on the first try.

cylaptor

then first replace the air filter and clean the LMM sensor with spray for the LMM sensor

JohnLane

OP your ‘84 500 SEL will have K-Jet for fuel injection. First thing to do is find a competent mechanic who is familiar with the car. Jethrow who can’t figure out a simple misfire is not going to be your guy.

Misfires.... Can be fuel, ignition, vacuum leaks (false air) or mechanical.

It is plenty old enough to be having issues with any of the above.

cylaptor

why would he need a good mechanic for a K-jet in the first place if it is one of the most demanding carburetor adjustment systems, then actually all owners of these models would need it, but they clearly don't have it. The problem is not in the K-jet

JohnLane

Maybe. Rather difficult to tell when we are not the guys doing the diagnosis. We can merely make suggestions.

You’ve not seen issues with K-Jet?

JohnLane

OBD I was mostly worthless. I have the tools to query it.