Just wondered if you had any idea on what to look at for a rough idle? When you first start the car when cold it seems fine, but after it warms up usually need to pump the excelerator peddle to get it started?

This is a hot start problem. Somewhat unusual with the CIS systems, but in this case, you are probably looking at a new enrichment compensator. They are usually about $375. While you're at it, you might as well replace the injectors as well. I think they're about $28/each from MB. Hope this helps. Oh, by the way, make absolutely sure you are running the highest octane fuel available, preferably Shell 93 or Sunoco Ultra 94.


------------------
Rgds,
Aaron Greenberg
MB technician
'67 250SE Cabriolet
'77 450SL
'79 6.9
'79 6.9
'80 300SD
'81 240D
'85 380SE
'89 420SEL
'93 300E 2.8

I had this same problem with a 1974 450SE. There is a cold start enrichment valve which is probably remaining open after the motor heats up - thereby continuing with an overly rich mixture which fouls the plugs. Check the plugs - if they are gas fouled it may be your problem. The valve was cheap and easy to replace.

------------------
Abe
1970 280SL
1974 450SE
1998 E430
2000 E55

The 74 and the 78 have different fuel managment systems!! I agree with Aaron on the warm up compensator.
After you check it we can get you one.
We can ship them anywhere via partsshop.

------------------
Benzmac:
1987 16V
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM

Sometimes I get the older cars mixed up but isnt the 78 450 SEL ( 116 chassis), an Electronic injection system, therefore it does not have an enrichment compensator. The enrichment comp. is only used on CIS cars.
I believe CIS was introduced in 84 on the 201 chassis with a 102 or 103 engine.
Now on the 78, if it is electronic injection, enrichment is done through Injector open duration via the engine control computer.
The first thing I would check is to check fuel pressure at rest and make sure its not leaking ( either an injector or the regulator).
hope this helps!!!

CIS was used on '76 and later V8s, including the M-100 (450SEL 6.9). Cars pre-'76 suffer from vapor lock problems. Not fun to deal with and a major pain in the butt! This injection on the early cars was known as D-Jetronic, and on '76 and later was K-Jet. And in 1980, the final year, came K-Jet with Lambda. Finally, the continuous injection systems (CIS) were as follows: K-Jet, K-Jet with Lambda, KE-Jet, and KE-Motronic. So Justin, I believe you are wrong in your thinking. Hope I have clarified this.

------------------
Rgds,
Aaron Greenberg
MB technician
'67 250SE Cabriolet
'77 450SL
'79 6.9
'79 6.9
'80 300SD
'81 240D
'85 380SE
'89 420SEL
'93 300E 2.8