Questions:

1.- Have the engine harness ever been replaced?

2.- Have the ETA harness ever been rewired?

3.- How many miles ago where the distributor cap and rotors replaced?

If the answers to questions 1 and 2 are unknown or no, all bets are off until fixed/replaced. Then move to question 3.

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1999 Porsche 996 Carrera Convertible
1994 420E - SOLD
1986 300E - SOLD, what a car
609 Certified

1. Don't know if the engine harness was replaced, but I think yes. The injectors have solid insulation. Although I only owned this car for 6 years, the car is 17-years-old, I would think the original harness would have failed some time ago. How to make certain?

2. If the ETA harness is what connects the starter and oil level sensor to the connection point between the control module box and firewall - Yes, I did it recently (and wrote the DIY article).

3. I changed the caps, rotors, and plugs about 5k miles ago, all Bosch. I just checked the plugs and they look nice and brown. I am planning to open the distributors and look regardless, and measure the resistance of the 10 wires. I just replaced both coils, but did not help with the symptoms.

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2004 E500 4Matic 138,000 miles

I started the car again, now for at least 15 minutes. On pin 7 (ISC) I got a code 10 (Engine speed (RPM) signal (TNA)).

I checked the resistance of the ignition wires between the coils and distributors, they are about 2 Ohms. The coil for the driver side bank does not snap as positively as the other when connecting the wire, but I am pretty sure it connects. With a timing light I see intermittent misses on the driver side bank. All seem firing, all with intermittent misses. I hope this makes sense with the code above.

I removed both caps and found some minimal oily layer in both, and cleaned them. Is there supposed to be a gasket or o-ring under the cap?

I checked wherever I could and found NO bad insulation. Everything seems solid. All sensors at the front of the engine, the harness at the brake reservoir, the harness going at the driver side fender has a slit and all wires inside are solid. Unless I missed another place to look, all are fine.

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2004 E500 4Matic 138,000 miles

I am thinking of a bad CRANKshaft position sensor. The ignition is triggered by it, which seems intermittently cut out, according to my timing light. Engine speed is determined by it, and I have pin 7 (ISC) code 10 (Engine speed (RPM) signal (TNA)). In the past, at times, I had engine wanting to cut out when coming to a stop, and I had to place the car in Neutral and rev it with the gas pedal. The cruise control stopped working every few miles, and was not working smoothly, giving small surges. Searching the forums, I found others who solved their engine runs rough problems with replacing the CRANKshaft position sensor. I don't have an oscilloscope to verify its signal, but based on the above, I think the CRANKshaft position sensor is a good replacement candidate.

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2004 E500 4Matic 138,000 miles

You need to check that the wiring harness has been replaced . . . it could (and does!) cause all of the symptoms you are experiencing. Check the w/h leads going to the CTS sensor; you can see if there are any frayed wires. If so, that's the FIRST thing that must be replaced.

The CKP is a magnet with wire wrapped around it . . . it's a passive device so if it's not been "hit" (to cause physical damage), it should be fine. An ohmeter should measure around 800 ohms +/- 400.

The "plugs" . . . hopefully they are Bosch copper plugs . . . not platinums! Those do not work in your MB.

If the w/h is good, then the codes point to a "going-bad" ETA detailed in Menu#24 http://www.k6jrf.com/MB_asr.html. Also in that path is the Neutral Safety Switch (S16/3) and it will cause the same problems. However, the ETA normally does not cause rough idling and/or stalling!

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Regards . . . . JimF
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'94 S500 Cpe

Visit my Mercedes Web Page

Nobody responded to your post 17 / #2, but ETA is the electronic throttle actuator, in the top center of your engine with a butterfly valve, the third wiring harness prone to crumbling insulation. The wiring is not a separate harness but integrated into the part, which is an expensive part. You'll have to open it up a bit to check it but quite easy to rebuild if you find it has wiring insulation problems. That would be my next step. What happened with compression test?

I will check the ETA and CTS wiring tonight. Then measure the resistance of the Crankshaft Position Sensor. I have not had a chance to do the compression test.

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2004 E500 4Matic 138,000 miles

You were quite correct, the ETA harness (cable) is in horrible shape. The insulation is cracked and in some places reduced to powder. I will post photos tomorrow. What options do I have in terms of rewiring or buying another unit?

The CTS is fine at least when cold, measures the same diagonally both ways. The Crankshaft Position Sensor is about 800 Ohms.

Yes, all ignition parts, including the spark plugs (F8DC4) are Bosch.

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2004 E500 4Matic 138,000 miles

Andras,
Sorry to read that . . . but the symptoms were tell-tale esp the non-firing/missing cylinders as well as some of the codes.

Check out Menu#24 for sources of ETA repair; some will take yours and issue a rebuilt unit; some will take your ETA and rebuild it. Of course, you can buy a new one but the price tag is high.

You can rebuild the ETA internal wiring yourself . . . if you're REALLY good at it but only a few can say they successfully completed that task.

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Regards . . . . JimF
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'94 S500 Cpe

Visit my Mercedes Web Page

Failure of non-ASR throttle actuators is extremely rare. They are much more robust than the ASR version. But check the wiring - it can go bad. And clean it up. Forgot to mention that your upper engine wiring harness should have a part tag with an FD date, the date that it was made. The tag is near the source plug behind the black box - should be able to get the number with a flashlight and a mirror. If it's a post production date you can take that issue off the table.

Jim,

I read your very interesting and helpful webpage. I called Beckmann Technologies and they would charge $1,200+ for rebuilding my ETA. I am shocked, and don't have the budget for it. Given the age and mileage of my car I don't know if I should even attempt rewiring, because there may be other worn or defective parts inside the ETA.

I'm just glad that I figured out what's wrong with my car with the help and guidance of all who replied to my thread. Thank you deanyel, pesuazo, and Jim!

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2004 E500 4Matic 138,000 miles

Andras,

As deanyel wrote, it could be just the internal wiring that is causing the problem so fixing that may get it running again. However, in my experience, the magnetic clutch fails (mine was burned out!) and that is a fairly common failure. Also the "REF POT" fails b/c it wears in spots and becomes intermittent.

There are other sources that are much cheaper than Beckmann so you could consider trying one of those. Prices are considerably less.

Pete Mahar S600 site (Uber Alles) has some detailed info on ETA repair. It is for a "dual" ETA car, a S600. The wiring is shown with detailed pics and it's worth a look.
http://w140repair.com/ETA_Rewire.htm

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Regards . . . . JimF
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'94 S500 Cpe

Visit my Mercedes Web Page

Thanks for the links. Yes, it seems straightforward enough to rewire. I have almost every tool, and even some of the wires in the garage. I need to buy the sheating, as I only have the GM-type slit wiring loom in the garage. I'm surprised they use solder rather than crimping in the ETA, right on the top of the engine, and it doesn't melt. Since it's a non-ASR, as deanyel pointed out, I am hopeful. I think my time and effort is a good risk vs. any alternate cost and vs. the benefit of having my car back.

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2004 E500 4Matic 138,000 miles

I successfully removed the ETA in 2 evenings, totaling 4 hours. JimF's page http://www.k6jrf.com/MB_asr.html was very helpful, especially the diagram and the warning about the spring running away. I grabbed the spring with locking pliers prior to removal. The vent hose (29), connecting hose (31), gasket (36), and at least one bolt (38) will need to be replaced, because they broke during removal. Next is cleaning, disassembly, and taking many photos.

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2004 E500 4Matic 138,000 miles

I finally finished with my ETA rewiring. When I connect the ETA and turn the ignition on, it will not hum, only jerk the butterfly valve once. Is this normal? I am afraid to reinstall it, unless I know it works.

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2004 E500 4Matic 138,000 miles