Replacing harness today.

[bimmerman]

I am replacing the harness on my 93 400E today along with the breather hose (which is in the way) that comes off the right hand valve cover. MY QUESTION: How do I access the lower end of this hose to remove and replace it? It seems to disappear down behind the throttle body on the intake manifold somewhere. Please don't tell me I must remove all that stuff just to replace the breather hose (which is hard as a rock and will dis-integrate when I try to remove it). GRRRRRR! Thanks for your help.

Garry
400E
635
735

[h_shek]

can't help but have you looked??

http://www.peachparts.com/Wikka/M104WireHarness

[bimmerman]

Yes, I had looked at that but it is for the six. I have the 4.2 V8. I was able to get the old harness off and the new one on in less than two hours. Car ran fine for twenty minutes then started doing the same old thing (losing power). I was hoping to get some expert advice here but nothing yet. Thanks.

[joe p]

Explain "losing power" Does it drop into limp? In other words do you lose idle control (idles about 450) and does the gas pedal feel unresponsive until about 1/2 depressed? If so, thats limp home. If you pull can codes, odds are one of 3 things are bad.

1) EA
2) E-gas
3) switch on pedal, unplugged, DOA or corroded connector.


There are tests for all of these, find someone who knows the system locally and let them fix it. These are high dollar parts and tossing peices at it is not the way to go.



Joe

BTW, the passenger side v/c vent runs to the EA and the hose is 3 pieces.

[bimmerman]

Joe P. I guess it would be called the "limp home" mode. I thought the new harness would fix it, according to posts I had seen on the board. Yet I drove it for an hour yesterday and it was fine. It is still an intermittent problem. Here are the symptoms: Car starts easy and runs perfect for a few miles until it reaches operating temperature. I pull up to a stop sign and then as I take off it stumbles and hardly runs, even though the gas pedal is about halfway to the floor. Then, after creeping along for a half block or so, it surges ahead with what feels like normal power. If I had a shop manual on this car I could likely find the problem but just guessing about how Mercedes does engine management things is sort of flying blind. Sure a different approach than what I am used to (BMW). Thanks for your thoughts.

Garry

400E
735
635

[stevebfl]

So BMW uses the same system, apply what you know from BMW and fix the car.

If you were working on BMW the only difference would be that you would have to have a $20,000 scanner to get the wiring diagram or diagnostic info, unlike MB which publishes such. You would still need some sort of scanner to talk to the car but only a BMW scanner would include the unpublished info.

Building motors is childs play compared to dealing with these kinds of problems. I have read this and the other thread about ASR and I'm at a loss to help. You have no tools (not MBs fault), and you have no info, (definitely not MB's fault).

Your cheap shot comparing BMW diagnostics, got my keyboard in gear.

[bimmerman]

Steve: Thanks for your comments. No, the BMW system is completely different than the way Mercedes does it, and is much simpler to understand. BTW, I can get the codes from my 635 Bimmer without any BMW propriatary equipment, although you can't do this with the newer ones. Sorry you took my comments as a "cheap shot" and I apologize if there was any offense taken. Certainly not intended. I am an M.E. by profession and enjoy doing my own work but I get a little miffed sometimes at the way the things are done these days. I recall something a Dealership owner told me a few years ago: "The only problem with those people in Munich and Stutgart is that they are knee deep in engineers". I guess I am still a believer in the K.I.S.S. philosophy! Thanks for your post.

Garry

[stevebfl]

I replied because your "cheap shot" comment reflects a misunderstanding of "why" things are as they are.

The single/dual throttle, drive by wire, system probably was first used on BMW 12cylinders in about 1990. The BMWs you mention are a different generation of technology.

There has been much talk recently in technician forums about legislation before the US congress. Originally the legislation was promoted by repair shops that were having trouble accessing technical info. An agreement came about a little over a year ago that was signed by 20 major manufacturers. It is called the NASTF agreement (all German manufacturers signed except Porsche). http://www.nastf.org/

There is a continuing effort to legislate promoted by the equipment manufacturers that would have the car companies responsible for documenting their design criteria. Some that argue for this argue that the car is too complicated. They argue that the car shouldn't be smarter than their level of comprehension. This is wicked arguement as there are some rather dumb techs and even dumber DIYer's.

This arguement seems to be mirrored in your judgment of the situation. It seems to me that many would legislate that cars should be no more complicated than could be repaired by DIYers in a home gargage with $2000 in tools (my aren't I generous).

Personally I love the technology and would hate to have to drive a 635 again. I have driven two different 540i E39 cars for the last 4 years and drove a 928 from 1987 to 1999 (still have it). I'm a big technology, v8 automatic, kinda guy.

[bimmerman]

Steve: I think your argument is a very good one and I am not really in disagreement with it. I owned a 740 for a while and found it a very exciting car to own. Much smoother and quieter than the big sixes. I guess part of my problem may be with the suppliers of many of the parts that go into these cars when they are assembled. To use BMW as an example, these cars were produced year after year with the same shortcomings. Driveshafts should last a whole lot longer than 50-75000 miles, as should heater cores, to use just two examples (I have had to replace these items several times on cars I have owned). I guess what I am trying to say is simply that for what these cars cost one should not have to contend with the same recurring problems. The guy who got me started with Bimmers back in the early seventies still has the 1984 733-i he had purchased new. It just turned 400k miles. Original driveshaft, three clutches, one valve job. That's all. Find me a newer rendition that will do that and I'll eat it (well, maybe not). BTW, your point is well taken about there being many poor techs and poor D.I.Y's out there.

If I lived in your neck of the woods I would bring my 400E to you to fix. Thanks for the discussion.

Garry

[TimFreeh]

bimmerman

How is the "drive by wire" system used on the early 90's BMW's different from the setup used in the M119 V-8?

I'm not well versed in BMW electronics but its my understanding they have pretty much the same components and the same basic theory of operation.

I also have a 93 400E with the EA setup. I've done a little reading on the system and I fully agree with Steve. If you don't have the equipment to read the codes and understand what they mean you are pretty much flying blind. This excludes hack mechanics like me from ANY troubleshooting/repair of components assocaited with the CAN.

BTW the wiring harness used in the EA is also prone to wire insulation problems. Mine was repalced at 37K miles by a prior owner - it failed long before I replaced the main FI harness at 105K miles. You might want to check the insualtion of the EA harness.

Good luck - Tim

[bimmerman]

The "drive by wire" idea in BMWs only came about recently. I purposely don't have anything newer than 92 (the last of the big six E32's). They don't use it. There is quite a difference between the throttle body assemblies on this vintage BMW and Mercedes. The BMW'w use a more common air flow meter/mass flow sensor which incorporates a flap in the inlet which is tied to a pot to tell the ECU where it is. I have seen this system on many import cars. The butterfly valve in the throttle body is directly actuated from a cable attached to the accelerator pedal. The cruise control is also attached to the throttle body with a similar cable. No electrical devices of any kind. It is simple, straight forward, and trouble free (and you can remove it in ten minutes). I like simple. I also like and appreciate new technology as long as the parts are made to last awhile. Everything is "outsourced" these days and I suspect that is part of the reliability problem. The bean counters will hate me, but if a manufactureer can save a few bucks per unit, times thousands of units, that is all they look at. That mentality used to exist only in Detroit but I can see it has spread elsewhere. Enough babbling from me. Thanks.

Garry

[bimmerman]

Tim:

BTW, where is the wiring harness located for the EA (whatever and wherever that is)? Thanks.

Garry

[Kebowers]

EA is the 'electronic accelerator', which is really the throttle actuator--the gizmo that opens and closes to let air into the engine. It is an electronically controlled electric motor coupled to the throttle butterfly shaft. It has a position sensor (variable resistor) for the throttle(accelerator) position, and another variable resistor (position sensor) for the throttle butterfly shaft.

You push on the accelerator--and first a micro switch on the top of the accelerator pedal opens and signals the 'engine control unit' to couple the 'electronic accelerator' motor to the throttle shaft (there is an electromagnetic clutch that disengages at idle or any time the computer says 'tilt'.)

The the EMU/EA checks the position of the throttle position sensor, checks the anti-slip, ESP,ABS systems, and determins if the throttle needs to be opened. If -yes-, then the EA computer sends a series of pulses to the EA motor, which rotates the throttle butterfly open. During this rotation, the EA/EMU checks the actual position of and speed of opening of the throttle butterfly shaft. This continues-always checking first, then opening the butterfly more-until the measured opening agrees with that commanded by the accelerator pedal. The EA/EMU then holds that throttle opening until the accelarator pedal moves (or one of the other systems like engine overspeed, transmission shift computer,transmission torque limiter, ABS,ASR, ESP calls for a reduction in throttle/torque/engine speed.

Fully closed to fully open takes less that 200 milliseconds. Open to closed is faster because the butterfly shaft is spring loaded to close.

The computer system has lots of safety features built in to prevent 'uncommanded throttle opening' that some cars seem to experience. Frankly, I don't see how it would be possible in the MBZ system unless a least 3 systems failed simultaneously--the accelerator pedal switch, the throttle (accelerator) position sensor, and the throttle butterfly shaft position sensor, AND the electromagnetic clutch beteween the throttle motor and the butterfly shaft.

A simple wiring short won't do it because the accelerator position sensor has a known range of values, and changed from (low to high) on pushing down on the pedal. The actual butterfly shaft position sensor has a different range of values, that changes in the opposite direction, so the system would detect the fault as soon as it a hppened and open the electromagnetic clutch.

[bimmerman]

That is a very well explained operational sequence, and I think I actually grasp it now. I had guessed that there had to be some type of electric clutch on the butterfly because if you shut everything off and move the throttle linkage it opens and closes like a "normal" setup. I had stated in another post that I consider a design as complicated as this (just to open the throttle) an over engineered "kluge" and I am glad my Bimmers don't have it. But then, I don't care for "fly by wire" aircraft either (A-300, Paris Air Show crash). Years ago I worked for the Seeburg Jukebox Company. Their motto: Simplicity, reliability, endurance. That works for me. Thanks for your comments.

Garry