Here is latest on my '08 ML350.
In the morning when engine is started and after about 5 to 10 seconds later it will stutter for a second or two and then smooth out. This stutter feels like engine might stall, RPM drops briefly but smooth out quickly and doesn't happen for the rest of the day. When weather is warmer, we had brief heat wave about a month ago (@65-70F), it doesn't happen.
I changed all the plugs and coils, plugs look clean, it was due for new plugs(200k miles). Other than this morning hiccup car runs fine. My mpg is about 16 in town.
Any comments?

 

I can only guess that it could be a fuel delivery problem.

On the next cold start, turn the key to pos. #2 and wait 5 secs. then start the eng.

 

Thanks, I'll try it tomorrow morning.
What do you think it is, fuel pump or fuel injectors?

 

My guess would be fuel pump or fuel filter.

 

OK
So after waiting 5 seconds it started fine and no hiccup. Is this mean that my fuel pump is slowly dying?
Car did ran out of gas several times and had to call AAA.

 

When did you run out of gas several times?

 

Sorry for the late reply.
It happened about 3 yrs ago and another one last yr.
Wife was driving and wasn't paying attention to gas gauge.

 

Did you try my suggestion in post #2?

On the next cold start, turn the key to pos. #2 and wait 5 secs. then start the eng.

 

Yes I tried it and it doesn't produce that hiccup (post #5)

 

Well that means that it is your 12 yr. old fuel pump or the filter.

Being that they are separate parts but attached together, you have to decide which to replace or replace both.

 

Thanks, I'll try to keep eye on it for worsening symptoms.