Rough Running R129 SL 500 in heavy traffic

[axj]

I have noticed after the car starts from cold that after a few miles in heavy traffic the engine seems to lose power at low revs and runs rough.Maybe around the time the auto choke in the injection system starts to switch off ?

Strange thing is after letting the engine cool down after having parked it for a few hours it then runs perfectly on the same length of journey back home.

The rough running is still there even if the car has had a thrash on the motorway a few days before, so its not something really associated with the engine just driving in traffic.

Engine is fine after getting over this issue once it has been driven for more than 20 minutes and is not running at low revs/ traffic - any thoughts from anyone who has had a similar experience ?

[ras62]

You dont say what year the car is but I would advise going to your local indi and have them read the engine fault codes. I would suspect a coil failure but it could be any number of things so before throwing money at it get some proper advise.

[xspencex]

Different car but my sisters C-Class did exactly the same thing. Mass airflow sensor was the issue, problem solved after replacing it.

[axj]

Thank's for the replies thus far....it's a '95 model i.e. before the mid -90's face lift with the new gear box, Air Conditioning controls and I think fold away mirrors & new alloys.

[r129sl]

Sounds to me like the (twin) distributor caps and rotors. Either worn or full of moisture or both. Not an horrendously expensive fix as these things go.

[Lord West]

I agree sounds like the dizzy's and rotas. Take one off and have a look. You WILL be able to see if it has a problem !. Its a quick job and you can even get pattern parts (BERU?) from places such as all parts which are half the Merc price.

[dickyf]

try running injector cleaner through it, merc specialsist advised me to do the same and it worked a treat.