M103 sluggish on high load acceleration? Tech Help Pls!

[appatula]

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.

[stevebfl]

Is it running in closed loop?

[appatula]

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!

[stevebfl]

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.

[appatula]

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

[stevebfl]

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.

[appatula]

All I can say is, beautiful explaination! I love how these cars engine management systems are very intricate, yet in reality, very simple. Therefore if I have adjusted the mixture to the proper duty cycle (via diagnostic pins 2&3) with a suitable DMM with duty cycle function, and/or a oscilliscope for visual affirmation could I assume that I am in closed loop? However, if I assume that this constant "fine tuning" is a result of the input from multiple sensors what if one of these sensors is not within spec. or malfunctioning? Would I then consider this to be a open loop situation because the engine management systems fine tuning would now be correcting improperly from the incorrect reading(s) of the faulty sensor(s)? How would I pinpoint the culprit if my previous assumption is true? Again, I appreciate your help Steve.

[Mike Freeman]

Appatula;
I've been working on Mercedes Benz for almost fourty years and I've never heard any 103 powered car described as powerful.
Perhaps before you do any more to your car you should go drive another of similar age!
Mike Freeman

[appatula]

Originally Posted by Mike Freeman

Appatula;
I've been working on Mercedes Benz for almost fourty years and I've never heard any 103 powered car described as powerful.
Perhaps before you do any more to your car you should go drive another of similar age!
Mike Freeman

http://www.peachparts.com/300e.htm Second line, sixth word in . All jokes aside, a 3 liter 6cyl engine should have more pep than I'm feeling. When I drove a 1993 5 speed 1.8L Civic LX there was'nt much difference other than a bit more power with the M103 and that bothers me. I've also ridden in a friends 300E 2.6 in which felt MUCH more peppy, I'm not looking to unleash the power of my 911 into the W124 but I know for sure something is wrong. It's embarrasing when I floor it into overdrive to make a swift pass and all the car does is rev into the 4-6k RPMs while I sit there and creep up like I'm giving it half throttle, something has to give here. I also note when it is in the higher RPM's under load it almost feels jerky and I can hear an uneven popping or choking from the exhaust. Although Steve may have pinpointed the culprit as being a A/F mixture component.

[appatula]

Any links to test procedures I could perform to narrow down any possible culprits?

[amg280]

Having owned one in the past, two things I would verify.

1. Are the cats plugged? That will kill all top end power, and the engine will just dwindle in that range and have not much output.

2. I had a bad o2 sensor in mine, and it made it feel quite sluggish.

Im assuming your fuel pressures are ok.

As for the M103's being slow, I disagree. They definetely utilize all 177 ponies to the max. In a drag race with my friends 88 300E vs my 92 400E, he killed me to 50mph, when I just started to pul ahead. Properly running, they are peppy.

[appatula]

Originally Posted by amg280

Having owned one in the past, two things I would verify.

1. Are the cats plugged? That will kill all top end power, and the engine will just dwindle in that range and have not much output.

2. I had a bad o2 sensor in mine, and it made it feel quite sluggish.

Im assuming your fuel pressures are ok.

As for the M103's being slow, I disagree. They definetely utilize all 177 ponies to the max. In a drag race with my friends 88 300E vs my 92 400E, he killed me to 50mph, when I just started to pul ahead. Properly running, they are peppy.

I agree 100%. Also thanks for chiming in, I really do appreciate help from the wise "Old timers" as I am just a youngster looking to learn. I bought a new cataylitic converter from Catco (Non-Calif Emissions Type) about a year and a half ago, however, since then I have done adjustments to the A/F mixture, would it be likley that errors in the A/F mixture adjustment plug my cat up in that span of time?
Good suggestion on the O2 sensor, I'm going to pick up a new 3 wire mustang O2 sensor at Pepboys and solder that puppy in. I also am going to pick up 6 new NGK plugs, as my previous A/F tuning mishaps have most likley taken a toll on the plugs.

Thanks again, any other suggestions are more than welcome here!

[amg280]

Originally Posted by appatula

I agree 100%. Also thanks for chiming in, I really do appreciate help from the wise "Old timers" as I am just a youngster looking to learn. I bought a new cataylitic converter from Catco (Non-Calif Emissions Type) about a year and a half ago, however, since then I have done adjustments to the A/F mixture, would it be likley that errors in the A/F mixture adjustment plug my cat up in that span of time?
Good suggestion on the O2 sensor, I'm going to pick up a new 3 wire mustang O2 sensor at Pepboys and solder that puppy in. I also am going to pick up 6 new NGK plugs, as my previous A/F tuning mishaps have most likley taken a toll on the plugs.

Thanks again, any other suggestions are more than welcome here!

Old timer? haha. Well I guess 28 years old isssssss getting up there.

I have had cats plug in less time than that (1.5 yrs). Especially if the mixture is off. That would destroy them pretty quickly. When the cats were plugged in my 420, the car still had alot of low end torque, and was really quiet.

[appatula]

Originally Posted by amg280

Old timer? haha. Well I guess 28 years old isssssss getting up there.

I have had cats plug in less time than that (1.5 yrs). Especially if the mixture is off. That would destroy them pretty quickly. When the cats were plugged in my 420, the car still had alot of low end torque, and was really quiet.

Haha, I'm enjoying the last year of my teens so I suppose I'll be "getting up there" as well Sounds like my catalytic converter may be a possible culprit Damn things are so expensive too! If I do end up taking it out, its going to stay out, as Connecticut does not require emissions testing for vehicles over 22yrs of age. Any other ways to confirm a plugged cat?