Faulty Wiring Harness, etc...

Change the plug connector/resistors under each coil. Short $$$ [ $10 ea] Car has Waste Spark ignition and when the plug connectors fail, they will skip on 2 plugs as each coil ignites 2 cylinders in series..

Beru are better then Bosch

There were problems with the engine wiring harnesses whereby the insulation cracked and fell off causing shorts etc. Lousy insulation but may owners got stuck on this account. M-B buys this stuff and doesn't seem to test it sufficiently - part of the less than good reliability they (and we) have with these cars. Correction is always after the fact, M-B should learn from Toyota whose cars don't seem to have such quality problems.

Toyota finally settled its engine-failure debacle with US owners whose engine clogged up with oil deposits and failed despite being maintained properly. They has spent years stonewalling the customers, as Mercedes has done regarding the Delphi-produced wiring harnesses.

Bill Ditmire Ditmire Motorworks,Inc.

MB service techs are saying that you can thank our tree-hugging friends for this bit expense. MB changed insulation and other plastic specs to meet new regs in Europe...specifically regs that specify a decomposition life span. The engine wiring harnesses meet that specification with a vengence.

The decomposition lifespan of the bio-degradeable insulation was not sufficiently tested under the same conditions as under-hood heat envirorment. One would think that a Co with such a Tech reputation would at least just simply do a recall and get it over with.. but....

To the Group:

Thanks to all for your responses!

We'll this is the latest on my Merc problem....I had the car towed to MB, they looked at it for 2 days and said that they can't find anything wrong with the car....Yes their diagnostics show that now, as before (see original post) cyls. 1 and 6 are misfiring, but this has, in their words, nothing to do with the previous problem where the same cylinders were misfiring, etc. etc. Anyway, their service manager is threatening to pull the gear box/ring gear because he claims he can't find the problem!? ...Gear box/Ring gear....am I missing something here. I can see a connection with the timing mechanism, etc. but it seems like they are grasping at straws...This is a re-play of exactly one year ago when the same thing happened. Now as before, I won't let them pull the gear box, etc. out of the car...Is there something more insidious here, like some other kind of electrical fault that I don't know about? They claim the ECU is fine!

Thanks!

He suspects one of the flywheel sensor segments... [ there are three]. that trigger the Crank Position Sensor. They are 120 degrees apart and each segment controls the HFM module [ ECU]

The easy test to check this is to use a dual channel scope-- one on the CPS and the other on the ignition low tension primary of 1 and 6. This will allow the tech to compare one against the other. If they are not in sink, that is the problem. I have seen this in an article , but not in any I have done.. The most common mis-fire codes on 104s is the plug connector resistors between the plug and coils [ all 3]. I mentioned that in a post before and I would just change them before condemning ring gear segments / CPS. We regularly change these with a plug change cuz of there high fail rate and low cost.

To the Group:

Again, thanks for the responses!

Here is where this ended....Merc changed the ECU and everything was better....they charged us about $2300!!! The ECU was one of the first things we mentioned when we spoke to Merc the first time. Given the history of the problem the ECU did seem like a possible contender. Also, given that the same cylinders were misfiring and that the wiring harness was already changed earlier in the year it seemed possible, at least to me, that the ECU could have been compromised by the shorted harness. Is this possible? The harness was changed at 63000 mi. and the ECU was now changed the same year after an extra 10000 mi were added? Can there be a 'glitch' created in the ECU because the wiring harness shorted, that EVENTUALLY caused a failure in the ECU or is this an 'all or nothing' type of problem....Meaning if the ECU gets fried it happens there and then and not after 10K mi?

In any event, we are arguing this with Merc via there complaints dept...

Thanks for posting this. I was just told by my dealer that I would have to replace the wiring harness at a cost of about $2K in the near future. (Had the car in for some other maintenance.) I'll contact MB and see what they say about "helping out" with this.