Hello,
I have a 2002 e320 with 131k. I am not a mechanic, and have done very little work on this car, but have replaced quite a few things on an older Lincoln I have (a different animal entirely). I decided to change the spark plugs on the Mercedes.
Initially I selected Denso 4503 / PK16TT, double tipped platinum plugs. I used the removal tool, did not pull directly on the wires, etc. All seemed to go (surprisingly) well. The check engine light came on when I started it after the replacement. Then, when I drove it, it stalled out at the 1st stop light. The pattern after that is it would almost stall out upon initial acceleration from a stop, and then take off fairly normally. It seemed a little less than optimum at highway speeds (like it didn't have everything it usually did to give).
SO, I did some homework, partially on here, and saw where some advised against the double-tip plugs, so I started over with NKG 7090 plugs (yes I am little bit frugal).
Much to my dismay - same thing; like as in no change whatsoever, right down to the check engine light. I will say with the Densos I reset the check engine light and it stayed off (but the driving symptoms remained); I have not reset it yet with the NKGs. I guess obviously I did not have anything like this before; the reason I changed them out is that I had a little rough idle at stoplights and just the mileage (don't think they'd been changed; not since I bought it with 84K).
Any thoughts on this would be welcome. PS- I do not have a code reader; I just reset the light by disconnecting the battery.