The only time that I am at this particular stop-light in the turn lane is immediately after I wash my car (get all water out of crevices). Every time I stop here at the red light, my C280 idle's roughly. Not jumpy or anything, just merely a rough idle. I always thought that it had something (?) to do with having just washed my car, until....
I was with my friend Lulu in her C230k at this stoplight, and her idle got rough @ the place (turn lane @ red light).

My question... is there a magnetic field or anything of the sort that can cause weird symptoms on cars, as I described??

It's so weird!

Thanks in advance!

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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!)