I just had the spark plugs replaced 2 weeks ago, coz of a dirty fuel tank and filters(changed the filters), the idling of the car was affected, the mechanic adjusted the air flow meter and went fine. But after a week of not using the car the idling problem appears again when in acceleration there is hesitations, like a choking feel. What supposed to be the problem? Any inputs will be great, thanks!

 

If the car has higher milage i would simple pull off the ingnition wire plugs one by one and isolate the problem..valve,fuel injector.
If this doesn't determine the problem ,back to the mechanic (not the same one..) to check for vacum leak and electrical stuff.
Good luck!
just a thought on adjuting the airflow meter..i am not sure about the w124 but on the 190,s the adjuster screw was sealed/riveted for a reason..

 

Reasons = Increase dealer service department revenue, and satisfy EPA requirements for new cars. They don't like adjustments hanging out on the open for people to screw with.

As the fuel distributor wears through normal use it becomes necessary to tweak this screw slightly to compensate.

 

due to carbon residue my spark plugs were fouled(changed) and just cleaned the cap and now it's good to go! Will clean and restore the gas tank, so hopefully this probs won't go back...

 

By the time the fuel distributor wears out , i don't think dealers even want to see a W124
But i'm looking forward to the outcome of this...https://mbworld.org/forums/e-class-w124/236315-300e-idle-mix-ok-but-when-revved-goes-off-scale-rich.html

 

Bad news, the hesitations came back after the cap has been cleaned, aside from replacing the cap with a new one, what other considerations to take to solve this probs of mine? thanks!

 

Sounds like your valve stem seals need to be done!!

 

Actually my valve seal has been done already, anymore inputs?

 

You said you cleaned the cap, what about the rotor?

I would replace them both if they are originals. Total cost brand new for them both is ~$75

 

The rotor is still good, might replaced the cap. Hope it will ran good good, coz I'm already planning on selling it...

 

Have you checked your coil?

 

Not yet, will looked into that. Will keep posted. Thanks!

 

Ignition coils are good, the mechanic just did something on the governor, and applied contact cleaners on the alternator, he thinks it's electrical, coz starting the car when not used for a couple of days will take about 5 secs before it cranks, and when doing reverse the response are slow. It's all good again. Anymore suggestions will be great! Next step for me is to purchase a tank retoration kit. Good luck to me...