I just occurred this problem today when I was on the way home. I was driving on the freeway, and I step on pedal to full-throttle, so the power kicked in, but about 3 seconds when is was still kicking in, the power just like "pause" 0.1~0.2 seconds and went back to "kicking-in" mode. so I am wondering if that is transmission problem? or fuel injection?

Doesn't sound like a transmission problem to me. If the car went into the lower gear and was going just fine, then it sounds like fuel was getting cut off, or something relating to a loss of power. My car does this periodically and I have heard that replacing the fuel pump relay is a likely solution. Good luck.

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2006 E350 w/ 155k miles (Daily Driver)

Previous:
1993 300E 3.2L Sedan w/ close to about 300k miles
2003 E500 Brilliant Silver (Had 217k miles when totalled!)
1989 300E with 289,000 miles (had for <1 yr while in HI)
03 CLK 500 cabrio (Mom's)
2006 C230k (Dad's)
1999 S420 (Mom's/Dad's)
2000 C230k Sport sedans
2001 CLK320 Cabrio (Mom's)
1995 C280 My First Mercedes-Benz... (155k miles. EXCEPTIONAL AUTOMOBILE. Was Very hard to let go of!)

so is there any way that I can test the fuel pump relay is bad? by the way, I haven't change the fuel filter for at least about 50,000 miles, is it possible causing this problem?

Pry the case off of the circuit board and look for a "cold solder joint" ie one of the terminals on the soldered side has a very small line around it (cracked). Just add flux and reheat with a soldering iron to repair. Brian

Slai,
I highly sugest you change your oil filter. That would very likely seem to be a possible culprit. Mine hadn't been changed in quite some time, and it resulted in a VERY rough idle that only got worse. Try changing it and seeing what happens.
NEXT, I would check out the relay. GOOD LUCK!

__________________
2006 E350 w/ 155k miles (Daily Driver)

Previous:
1993 300E 3.2L Sedan w/ close to about 300k miles
2003 E500 Brilliant Silver (Had 217k miles when totalled!)
1989 300E with 289,000 miles (had for <1 yr while in HI)
03 CLK 500 cabrio (Mom's)
2006 C230k (Dad's)
1999 S420 (Mom's/Dad's)
2000 C230k Sport sedans
2001 CLK320 Cabrio (Mom's)
1995 C280 My First Mercedes-Benz... (155k miles. EXCEPTIONAL AUTOMOBILE. Was Very hard to let go of!)

I think Dave meant the fuel filter, not the oil filter. Check both of them, the small inline - which you can blow out, and by all means change the main filter at least once per year as it can really reduce your power slowly when it gets clogged.

__________________
'76 240D-Sold
'78 240D-Sold
'85 300 SD, 165K-Sold
'88 300 TE, 165K-Sold
'64 Porsche 356C Cabriolet- under restoration
'86 560SL 124K Miles-Sold
'94 320E Wagon, 74K Miles-128K Miles JUNKED
'06 E350 Wagon, 84K Miles
07 SL550, 14K Miles

Yes Ron, I did! Thanks for catching that. I was really trying to figure out what you were talking about!

__________________
2006 E350 w/ 155k miles (Daily Driver)

Previous:
1993 300E 3.2L Sedan w/ close to about 300k miles
2003 E500 Brilliant Silver (Had 217k miles when totalled!)
1989 300E with 289,000 miles (had for <1 yr while in HI)
03 CLK 500 cabrio (Mom's)
2006 C230k (Dad's)
1999 S420 (Mom's/Dad's)
2000 C230k Sport sedans
2001 CLK320 Cabrio (Mom's)
1995 C280 My First Mercedes-Benz... (155k miles. EXCEPTIONAL AUTOMOBILE. Was Very hard to let go of!)

Mine did the same thing recently while the wife was driving it. Of course she totally freaked out and drove it immediatly to my independent. I got a call at work from him explaining that my wife was there with the car and that he had driven it approximately 20 miles trying to duplicate the condition (with my wife in the passenger's seat) but it did not duplicate. He explained that there is nothing to worry about unless it repeately does it or is accompanied by other problems (ie rough idle, ck engine light, missing, etc) and explained that although a MB is as close to prefection as one can get in an automobile (He loves his Benzes), they do "glitch" on rare occasions.

Hope this helps