Well, damn it, I'm here again to tell the tale of this high quality vehicle called Mercedes. Ugh.

On the last 20 mile leg of a 200 mile round trip, I had to slow for a right turning vehicle in front of me. As the cars behind me were coming up on me in a 70 MPH speed zone, I decided it would be nice of me to accelerate quickly to prevent them from slowing way down.

As I laid my foot heavily upon the accelerator, the engine hesitated and the car bucked. At this moment, the CEL came on. The rest of the trip home was down on power and the engine was clearly misfiring.

I'm suspecting plug wires, as the misfire seems pretty consistent. I've never seen plug wires hard fail like that though. Maybe the engine management system is running in limp home mode or something and it's amplifying the bad wire problem.

First thing to do is to get the fault code read and post them So we can inteprit them. You can get them read at most auto parts store.

It'll be at the dealer on Wednesday. I'll let them diagnose.

I had a similar problem. It was a bad coil. I believe there are 6 coils (1 per cylinder). Mine was covered under warranty.

Good morning all,

I am new to this forum and would like to introduce myself. My name is Ricardo. I live in Ann Arbor, MI. Have owned a MB for four years. Needless to say my MB experience has been rather ugly.

On to the engine and other things, try twelve ignition coils. two per cylinder.

I am having the same problem. Diagnosys says misfire on numbers 2,3 and 5.

In my case I doubt is the coils since the engine runs perfectly at least 5 minutes once a day, and this happens when the engine is first started, then 5 min. later is rough idle. I have heard it may be the MAS, so I messed with it a bit and the engine ran OK for about 20 minutes. then the rough idle.

I'll try to get the codes sometime this week.

Regards,

Ric
00 ML320 102k

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Ric
Ann Arbor
2000 ML320, 172k

If you think education is expensive, try ignorance.

Diagnosis was ignition coil pack. Covered under extended warranty.

They also said I have 4 bad plug wires. They quoted me $300 parts and labor for just the 4 wires, not all 12. Have you seen how short that wire is?

Since they are so expensive, you'd think they would last longer than 55k miles. If they did, I could very well see the expense. What exactly is it that they do that is so special that they justify such a high premium?

Saying something doesn't make it true as I'm sure you know.

What was wrong with the 4 wires they said were bad?

Ask them for the resistance reading of each of the old wires and then ask them what the resistance reading should be.

Yes, if you're wondering I'm skeptical.

I'm not skeptical. These people have been really good to us. When I said I wanted to replace the wires myself, he said "ok". I asked if that was a problem and he said, "no". No pressure to get it done. They are just high as hell price wise.

I had received a quote from them for $600 for front and rear brake pad replacement once before. I was stunned.

Break pad replacement for $600???? I did it for $250.

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Ric
Ann Arbor
2000 ML320, 172k

If you think education is expensive, try ignorance.

Ok, I FINALLY got it all back together again.

I measured the resistance values of all 12 plug wires and there were only two that were out of spec instead of the four that they told me. One was 2k, which seems acceptable to me and the other was 8.5k, which is the reason for the misfire.

A tip to the cost-conscious:

If you have a CEL and a misfire, pull your plug wires and ohm them. If you find one bad, you can order just the one from FastLane for $38.

I was going to replace the plugs, but could not find a good reference on FastLane, or at NAPA or AutoZone. They kept trying to sell me the Platinum 2 Bosch plugs and I just don't want to go with anything other than OEM.

I finally wound up at the dealership and got a price of $18.90 each!!!!! That's $245.50 after tax. Gimme a damn break! Needless to say, I appologized to the nice gentleman who pulled the parts for wasting his time and made my way to the exit.

I'm sure some of you are tired of hearing me moan, but this vehicle has totally ruined the MB brand in my mind. I can't wait for the mandatory extended warranty to be up. I only wish that we had been in a better position to trade up at the 50k mark.

Bosch makes the OEM plugs for MB and they are the platinum series so using the twin spark version is a perfectly fine replacement. They're $3.99 each. Lots of people have used them including myself and I can attest that my engine is smoother.

Very wise. To replace with non OEM is not worth the risk, at least to me, of a potential problem with a part as critical as a spark plug.

When I replaced my plugs I got them from Phillips, a MB dealer in Virginia Beach. The cost per plug was about $7.50 each.

I found that the ML320 engine (112 engine) has a system which in certain occassions it will turn on. This system is called "Cylinder Shutoff". This happens on many occassions (eg. going to fast, bad O2 sensors). When the engine goes to this mode, also called "Limp-Home" mode, cylinders 2, 3 and 5 are completely shut off. All kinds of misfires and tremendous loss of power.

I had this problem and took the car to the dealer. Mind you, I have 104k miles on the car so warranty is gone......The dealer's opinion on diagnosing the CEL was that they first needed to change the spark plugs ($500.00 cost) and also they needed to change the left cat. converter ($1750.00). They knew the engine was misfiring on 2, 3 and 5 and I knew the same because I had a friend pull the codes.

Now, I think the dealer was trying to pull a quick one.

Right now I ordered 12 new spark plugs and four O2 sensors...total $442.50.

Let me know if you need info on the "cylinder shutoff" condition. I pulled literature from the MB start tek web..

Regards,

Ric

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Ric
Ann Arbor
2000 ML320, 172k

If you think education is expensive, try ignorance.

Cylinder Shutoff (CSO) is a feature of the M137 V12 engine, and I believe MB may have removed this system from the US versions. The V6's and V8's don't have it. The engine can disable individual cylinders due to misfire, this is actually Federal Law that the engine does this in case of a misfire, but the engine isn't designed to shut off one whole bank as a "feature" of the engine.

Gilly

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Isn't the "limp home mode" a function of the transmission?