This has been a serious subliminal problem that I have been trying to blame on a poor A/F mixture however I have come to the conclusion that it is most likley something else. The car feels somewhat slow in general (Low end power has improved noticeably when I found the correct A/F screw position), not the powerful car it should be. This feeling intensifies 100% when I floor the car into overdrive, it revs but no power, no pull, and sounds as if there is a miss. I have replaced the distributor cap, spark plug wires, and spark plug wires around just before springtime this year. I also replaced the OVP relay to rid of irradic idle however this lack of power still haunts me. I know the M103 packs more punch, I'm almost leaning torward the valve timing. What do you guys think?


Also: I replaced the fuel filter in the past year.

Is it running in closed loop?

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

Steve, thank you for your post! I am a bit undereducated regarding the CIS-E injection however after reading some of your previous posts regarding similar matters, I believe you are basically concerned that I have a oxygen sensor working within the system. That is one thing I have not swapped out since I bought my 86' 300E, however, there is one in the car. Could this really be causing my troubles of high load, high RPM power loss? I was thinking that my issues were more along the lines of an ignition or valve timing issue . Also would you recommend the 3-wire mustang oxygen sensor retro-fit? Thanks!

My question is based on this statement: "The car feels somewhat slow in general (Low end power has improved noticeably when I found the correct A/F screw position), "

If you don't understand closed loop and how to measure it, you did not find the correct A/F screw position. What you have more likely done is overwhelm the control system and richen the mixture in a compensatory fashion. Basically you are adding to your problem.

The car works properly (fuel control related) when it runs in closed loop. For the most part it can't have a mixture problem if it is in closed loop.

That isn't to say you have a mixture problem, it is just the reason I asked the question.

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

Not sure if I understand how the closed loop methodology works, however I assume the sensors regarding EHA, 02, RPM ect should all be in connected in a closed loop? I measured duty cycle (Pins 2 & 3) via my handy Hewlet Packard Oscilliscope, A/F seems to be within spec.

Aside from the techincal tuning method regarding duty cycle, I have also leaned the mixture out until the car stumbles but still runs, and slowly richened the mixture with no difference to the high end, high RPM studder while leaned or while richening the mixture.

Again thanks for putting up with my ignorance

You aren't quite understanding closed loop. Closed loop doesn't represent a physical relationship, it represents a dynamic control theory. It is a control theory used in many forms of machinery or electronics. The purpose is to automatically maintain, observe and correct a specific issue, mixture in this case.

What takes place is that through the use of the closed loop cycle one adjusts the mixture to the middle of the correction range (this is for early cars, later cars do this themselves through what is called adaptation). then the cars management system monitors the actual mixture by viewing it's end product in the exhaust with the O2 sensor. It takes a rich mixtures signal and changes the control current to the eha which alters the lower chamber fuel pressure and finely adjusts the mixture. It does this until it sees a lean mixture. The range of movement of mixture is very very small. It is closed loop because it continuously monitors and corrects. It becomes open loop as soon as it can't correct.

If you are taking mixture to the point that you can feel a change you have seriously exceeded the systems capabilities. If the system were within its capability as soon as you adjusted lean it would go rich and repair your actions. Go futher lean and it will do the same. It will continue this till it has no more capacity to correct. Somewhere way beyond that point you will go so lean that you feel it. The point here is that if the system is in closed loop your mixture adjustments will not alter the actual mixture. All you will do is use up the ability to correct in that direction.

If you view this on a analog scale of one to ten, the proper set point for adjustment is 5. If you then make a lean adjustment the reading wll go to 6 or 7 (or more). This reading is only in closed loop if it goes lean and rich as it corrects. A proper set mixture would have the reading swing from say 4 to 6, or maybe 4.5 to 5.5. The smaller the cycle the better the control.

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician