Otherwise a terrific car, this car has had driveability problems for 5 years. Originally it would start and run fine until I shut it off. Then it would easily restart when hot but dog and quit when I tried to drive away, with the "economy" gauge deflecting fully to the right while it was dying. I had the O2 sensor replaced and the idle mix adjusted and that problem is gone but now it has different problems (immediately after the other repair). Now the idle speed oscillates between about 400 and 700 RPM with a frequency of about 1 time per second. I can feel this even when the car is in drive. Also, about half the time when I accelerate, it hesitates, sometimes a LOT, even if I accelarate from coasting at most speeds below 50 mph, to thepoint where transnission shifting is somewhat clunky. It appears that, if I wait until the rpm oscillation is at its maximum when I accelerate, it works fine but at low ebb it dogs. Also, it has a propensity to die as I pull up to a stop sign and stop. When it does that, I have to crank a long time to start it. Also, often when starting it hot, it now dies as the starter lets go and I have to crank a long time to get it to start again. When it does start, it runs fine with the limitations described above. It definetely appears to be an idle mix problem but no one here seems to be able to figure it out.

I have tried different gasolines, even the so-called "special" fuel for collectible/off road cars (no ethanol in it) with no difference. I always use top grade premium.

The Computer show no codes but the I/O port on that does not work anyway (the "check engine" light does not come on as it should with the ignition in the run position but engine not started, nor does the diagnostic port communicate with the tester - this has always been the case, however, since I have had the car.). The computer had been replaced once (prior to my having the car) with a "rebuilt" unit.

I have little or no faith in our locals because I also recently had a timing chain jump a tooth. Neither of the local MB shops could figure out what was wrong and I myself had to diagnose the problem for them so they could do the grunt work. (I cannot believe any trained individual could mistake the performance of a car with a timing chain off by a tooth with a distributor cap, $300, or poor compression, another useless $250 to test!) Likewise, in my last discussion with one of the local MB mechanics about this issue, his answer was "junk it". Not a very helpful reply to say the least. There don't seem to be many MB "Geniuses" here in Minneapolis/Saint Paul!

There isn't a pat answer to your problem. Both the idle control function and lambda correction function must be monitored to diagnose the problem.

How close are you to Moorhead MN? I know someone there, competent and patient enough to get to the bottom of your problem.

I suspect that you are one of the luckiest and thus unluckiest of V8 MB owners. In 27 years of V8 chain failures (well into the hundreds), I have only seen 2 that only jumped 1 or 2 teeth. Your occurance is thus a very rare occurance to an experienced tech. I'm not condoning charging for poor diagnostics, but I could see it taking someone off guard.

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Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician

Actually, Moorhead would not be out ofthe question, once I am moved into my new house.

I understand that these things are not all that simple to diagnose and, yes, I realize how much damage can be done in a timing chain failure! That is why I had the chain changed at 120,000 miles. But the plastic guide broke and a piece of it worked its way between the chain and the gear causing the chain to jump.

Thank you for your reply.

Chains are almost never the problem. When asked, I tell people to replace the rails every 75k miles and replace the chain or verify cam timing every 150k.

I was going on advice from John Olson, editor of "SL Market Letter" and author of two text books on the history of Mercedes Benz and of the "SL". Oddly, the local yokel at MB advised me AGAINST replacing the rails when I had them replace the timing chain because he said the rails should easily last until I need the next timing chain. Shows you what THEY know... The report on the valve timing, at the time I replaced the chain the first time was that timing was 7 degrees out on the right side of the engine. It also made a loud valve noise-like noise when I started it in the morning and that went away after the timing chain was replaced (until the LOUD noise when the chain jump occurred!). I tend to be quite conservative about service. I'd rather spend $500 now than $5000 later. I also change my oil every 2000 miles.