Hello,

For my 1989 W124 300E M103, I replaced all 6 fuel injectors (along with the holders, rubber o-rings that fit around the holders and the rubber cap) and the large rubber intake boot this past Friday.

I knew I would have to re-tune the mixture as during the first test drive, all prior issues of a slight hesitation were gone, but now my car would hunt for idle slightly when letting off the throttle to brake for a stop sign. (Repeatedly did this during this first test drive.) It even stalled twice, once when switching from R to D and once at a stop sign.

I brought the car back into the driveway, connected my DMM to ports 2 and 3 of the X11(?) connector and tried to adjust the mixture using the duty cycle feature.

CCW -> Leans out the mixture
CW -> Enrichens the mixture

Key in, ignition at position 2, engine not running the reading was 69.2%. (Federal controller = 70%, California controller = 85%)

Upon the first start-up without adjusting anything, my car started in open-loop with a reading of 49.4% and was rock solid during this time. Then shortly after start-up the car switched to closed-loop operation.
The number climbed from 49.4% all the way to 92.3% over the course of about 1-2 minutes and remained at 92.3%.

I started a process of turning the hex screw at the mixture tower CCW to lean out the mixture slightly, about 1/4 turn at a time.

I could never get the mixture number to stop climbing to 92.3%. After a few iterations of turning the mixture screw CCW (leaner) in 1/4 increments, my idle quality started to suffer. (It was starting to get to the point where my idle would be about 350-400 in R or D, the engine was on the brink of stalling.) I have a few things to attend to this afternoon so I just enrichened the mixture (CW) about 1/2 turn from my last setting to restore my idle quality and keep the car from stalling.

A short test drive and the car runs well enough, no stalling or low power, but it definitely running rich. (i think....)

What should I test next? Or am I not being sensitive enough with the adjustments? Does the EHA need to be adjusted now?

__________________
2006 BMW M5 "Heidi" @ 109,000 miles
2005 MBZ C55 AMG "Lorelai" @ 165,000 miles
1991 MBZ 300E "Benzachino II" @ 165,000 miles
1990 MBZ 500SL "Shoshanna" @ 118,000 miles

(On the hunt for a good used M103 engine as of 6/10/23, PM me if you have one to sell!)