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  #1  
Old 11-21-2002, 01:40 PM
jmdunn
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Question It has to be something simple, I've replaced about everything on my 450Sl

I am at the point of total frustration with this car.

History-
I purchased in January for $5000 from the original owner w/172,000 miles with all service records and a bad transmission which I replaced(lots of thanks to stevebfl and M.B. DOC)

symptoms-
Hard to start. terribly rough and fluctuating idle. In P somewhat smooth in D shakes and stammers or dies. Hesitates awfully up to ~2500 rpms (25-30mph) after that smooth as glass.

what I've replaced(sorry for the long list)-
fuel distributor - set to 5.0 bar system pressure
air slide valve, cold start injector, control pressure regulator,injectors w/ seals, holders and o-rings, plugs, wires distr. cap & rotor, coil, fuel filter, distributor vac. advance, thermo vac valve, catalytic converter. All vac. hoses and checked against diagrams from my CD.

What I've adjusted-
timing to 0 degrees (runs much better if advance 20-30 degreees)
checked that distributor was pointing to #1 plug wire when engine pulley is at O on crankshaft across from timing pointer.
set CO to 3% to make it keep from stalling in D
cleaned throttle body

I've spent a lot of money on this car and would like top be able to drive it someday. I know throwing parts isn't the correct way to fix or diagnose problems but withthe car being 25 years old a lot of them were safe bets for peace of mind if it ever gets running and WE can travel in it.

I would apreciate any suggestions,
Help me renew my faith in MB

jmdunn
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  #2  
Old 11-21-2002, 02:27 PM
michael cole's Avatar
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Join Date: Apr 2002
Location: waterloo ontario
Posts: 730
how did you adjust the co for 3%.do you have emission testing facilities in your area?they can test the co% very accurately.it sounds to me that the fuel mixture is too lean.you could try tweeking the mixture adjustment a fraction of a turn clockwise until the car runs well under load.hope this helps
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Old 11-21-2002, 05:34 PM
jmdunn
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I have an older analog gas analyzer that reads CO% and fuel/air ratio(14:1etc). I put the tester on my jeep to make sure it works.
On the jeep it reads about 4% which is high for a computer controlled electronic fuel injection so I adjust the needle to 1.5% for calibration and move to the mercedes. If I jump the mixture way up it smooths out but guzzles gas and coats the plugs with carbon. It is still very hard to start.

forgot to mention I checked compression and all 8 cylinders are from 125-133 psi.
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