If you were going to the doctor, they would ask you to fill out their medical history form.
This can help with diagnosis. You might consider doing the same thing.

The engine may have 180,000 miles, but what is the maintenance history. For instance, my '92 300E has 242,000 miles, but all the ignition components are relatively new.

You would probably be best served by simply making an appointment to have you car scoped at a MB independent shop. That will be more cost effective than throwing parts at the problem.

Steve

Easy check for engine model. M103 has round air cleaner , distributor cap and visible plug wires. M104, air cleaner rectangular, no distributor cap, no plug wires visible.

Steve

Hi All,

Thanks for the replies. Ferdman. Its a 103. The 104s and 103s had an overlap in the 300CE in Ireland around 90-91. Softconsult , yup, dont wanna throw parts at it, and thought I'd post here before taking it to an MB doctor. Cheaper again if I can fix it myself with some advice from here.

I posted without history as someone may have had similar symptoms or may have recognised the symptoms from experience.

I bought the car 3 and a half years ago at 147,000, no previous history.
150,000 replaced head gasket ), replaced valve stem seals.

160,000 replaced fuel filter, dist cap, rotor and wires (Beru).

175,000 miles began to notice the idling problem,
176,000 (approx) replaced airfilter.

179,000 replaced ignition coil and changed plugs (Bosch resistor). Old plugs were a good colour.

My next step is to get a set of NGK non resistors just incase. In addition the oil and filter are changed every 6000miles. (I usually change plugs every 2nd or 3rd service).

I have been doing very little mileage lately as I dont need the car that much(living in College, maybe its not being driven enough?).
If you need any more info let me know. Thanks
Gerard

Gerard, install Bosch F8DC4 spark plugs and see if that makes a difference in the idle.

Steve, the 104 engine in a 1991 300CE has a distributor cap and rotor. The 1994 and 1995 variety may have eliminated both and gone to 3 coils ... one per 2 cylinders.

__________________
Fred Hoelzle

Yes, and the early M104 engine in the 1990-1992 300CE's have a round air cleaner, as well.

__________________
Paul S.

2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".

[QUOTE=Ferdman;1437481]Gerard, install Bosch F8DC4 spark plugs and see if that makes a difference in the idle.

I'll have a look for them here (Ireland) and give them a try. Will report findings in due course.
Thanks
Gerard

Hi All,
Just to update on my idle problem.
The distributor cap was in very bad shape (happened a lot recently). The contacts were all that blue stuff that brass turns to when it corrodes. I replaced the Beru cap with an old bosch one that I had as a spare. Its running fine since.

I'm using resistor plugs at the minute, but will change to H7DC (as recommended in the owners book that lay in the car!!) when I have time. I've had a lot of trouble with the distributor cap this last 2 years. I wonder is it something to do with the car not being used enough?
Maybe I just have to clean the cap every now and then.

Gerard

Think you will find that correct plug is either H9DC or H9DC0. These may be in short supply if they are on the Bosch phase out list.

Steve