Mercedes-Benz Forum - View Single Post - M103 Rough idle and vacuum leak
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post #115 of (permalink) Old 01-11-2018, 09:41 AM
BenzWorld Member
Date registered: Apr 2011
Posts: 75
Mentioned: 0 Post(s)
Quoted: 19 Post(s)
ADMINS, any way to get "MB Engine Forums"? Too much good info spread across at least two forums as it is.

H.D., As I have only been introduced to your posts today, and have only had the time to read a few, I wonder if you have spent much time on the bottom end. My M103 and the one I bought at the junkyard both had enough bottom end wear to cause my oil consumption, which can slowly foul the O2 sensor leading to problems x,y,z..... With your systematic approach, I wonder where you place the bottom end in your list of things to check.

All, H.D. mentions checking the play of the AFM in an earlier post. The focus seemed to go to adjusting the height of the plate and its exact position in the aluminum body, but I didn't see enough stress placed on making sure the plunger in the middle of the FD was NOT depressed while the motor idles. Here is what I posted to the peachparts forum back in 2011 as an update to the head and CIS-E rebuild:

"My rich idle was the result of the fuel distributor’s plunger extending too far down onto the roller on the flapper. Adjusting the position of the roller with the 3 mm CO screw did not work for me. I could get the idle mixture correct but then something else went wrong: bad throttle response, hard restarts, surging idle, high RPM idle, etc. The rich idle could have been the result of the flapper spring fatiguing over time as well. Who knows? Bottom line, adjusting the plunger (moving it up into the distributor) about half a turn allowed the other parts of the fuel system to work as designed."
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