Stumbles off Idle - Warm or Hot
 

I have a 1983 Mercedes 380SEL that stumbles off idle. I have had many new/rebuilt parts including Rebuilt Fuel Distributor, Rebuilt Warm Up Regulator, New Distributor, new Rotor, new Cap, new HV wires, new plugs, new coil and new Ign. Ctl Unit. Didn't help a bit. It idles fine....very smooth, starts pretty good too...hits right off when cold or hot..sometimes idles a bit rough for a minute before getting smooth, especially when hot. I have had two outstanding genuine Mercedes service organizations look at it...with certified mechanics with over 35 years of Mercedes experience. All are stumped! External tests including HV wafeforms were fine. Line pressures were "ok". Internal engine tests (again by Mercedes dealer) revealed the internals of the engine were 'excellent'..very good compression, etc etc.

If you try a very hard acceleration off idle....the engine even dies! Any ideas????????

Respond to "LarryM3711"

I would be inclined to lean in the direction of a fuel related issue, either a lack of proper fuel enrichment or it is an electronic regulation matter. I believe Bosch referenced that system as the KA Jetronic.

Have you tried installing a new oxygen sensor and resetting the CO mixture? Might be a god start.

Personally, I avoid most rebuilt fuel injection components unless they are made available through Bosch or MB. I believe "spray and pray" rebuliders simply do not value time, be it theirs or mine.

Try a few treatments of MMO. It dissolves gunk in the fuel system in case anythings sticking. Some people don't believe in it but I do.

Did you change injectors?
 

I have had all the common idle issues and have replaced a lot of parts that have cured many problems. My car ran fairly well but I am compulsive. I changed the fuel injectors and it made a huge difference. But with that said, my car can surge a little but only at certain tempratures. It's not offensive like it was... A retired service manager from a large MB dealer in the area said "they never idled well". The earlier models with converters under the hood suffered vapor lock. If you can reproduce the stall it stumps me too. Your Ignition Control Module is new? Are all the parts you replaced to cure the stumble off idle? How many miles on the car? Clogged exhaust? I'm grasping at straws but you never know which far out idea... Who adjusted your fuel distributor?

380
 

All I have to say is thats a CIS 380 for you!

Good luck!

I got some of the warmup regulator and vacuum port functions explained to me in another thread. There is a green/white orifice that goes to the front port and it buffers the vacuum momentarily on acceleration. Might be worth checking. Did they share the system and control pressure readings with you?