Hi, as you can imagine, diagnosing a noise over the internet can be difficult. Having said that, one of the most common things that I find on the ML relating to a rattle on acceleration is a loose catalyst element inside the catalytic converter. When the catalyst breaks loose it will give you a rattle on acceleration. I'd have the converters checked for a loose catalyst element.

I'd have to suspect the converter for something like this. It's a rather common problem on the ML.

I do not think that it's an engine ping. There are sensors on the motor that correct pinging.

Unfortunately it is. The converters are in the $800 - $1200 range but lately Mercedes has come out with remanufactured converters that are very reasonable. You'd have to have the dealer check availability if you need a converter.

Yes it does, one on each side.

Without hearing it it's hard to say but I doubt that it's an engine ping. I assume you use premium fuel. If you are using a lesser grade I'd switch to premium.

95 is fine, you're octane rating must be higher over there. Premium here is 93.

I think that you should have them checked for a loose catalyst element.

No, they use a rubber mallet to bang on the converter housing to see if it rattles.

Correct, but it would be most unusual to have a rattle from the engine.

I do think that a loose catalyst element is the most likely cause. Without actually hearing it I cannot be sure but it's a pretty common complaint.

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Definitely not, if it was misfiring the check engine light would come on and most likely the computer would shut down some cylinders and the car would run rough after the misfire occurred.

Yes that is correct, when the catalyst is loose it tends to rattle on acceleration.

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