The other 3 spark plugs are under the ignition coils (no. 4).

__________________
--
Steven Harrison

1993 300E2.8 - 196K
2001 E320 4MATIC - 86K

That means the coils have to be removed when changing spark plugs? What a weird design .

__________________
1996 E320 since 1/16/08, 171K miles as of Feb 2011

---------------------------------------------------------
1989 300CE - R.I.P. Dec 29 2007
Other MBs (sold): 1992 300E-24 - 1979 350SLC - 1984 230E - 1990 300CE

i can see the picture a little better on my other computer, 20 looks like another part of a fuel lines,
the brake boster is the black plactic line that passes by the abs unit, and #3 isn't actually the maf sensor, but rather the maf plug

__________________
1967 250 S
1967 280SE
1968 250S
1971 280 SE
1973 220
1974 280 S
1975 450 SEL
1976 220 D
1979 300SD
1983 300 SD
1985 230 TE euro
1986 280SL
1986 500 SEL euro
1986 190E 2.3
1990 300 SE
2003 C230 K
2004 C230 K
1987 560SEL
1987 300SDL now in canada
2005 C230
1998 C43 AMG Sold to DON
1993 190E 2.6
300TD Former daily driver Totaled
current:
R320 CDI
Ram 2500 Cummins