My dad's 1987 (60,000 miles) 420 SEL developed a rough idle after I replaced the spark plugs the other day. It ran fine before I changed the plugs. I also replaced the cap and rotor. I have my suspisions that this problem is related to the Bosh Platinum plugs I put in it. (Bosh Tech support said that these plugs would work with this engine and that they have extensive testing to prove it, the tech support guy said my problem was due to a bad coil or wires.) So I tested the plug wires, they are Beru and say 1k on them. My results are as follows...

8 1.226
7 1.203
6 1.171
5 1.19
4 1.18
3 1.24
2 1.15
1 1.18

with the meter set at 2k

wire from coil to cap showed good continuity.

Should I replace the wires and or coil or just put the old plugs back in? They didn't look that bad, we just decided to replace them because I read 60k was a good time to do it...Or does anyone know of a better plug to use than the Bosh Platinum?

Thanks, Joe

__________________
1987 250D
1984 300TD
1983 300D
2002 Chevy 2500HD Diesel
1995 Dodge 12 valve Cummins Dually
All Biodiesel Powered