specking of replacing so tune up items. I can not get the spark plug ends to loosen on the distributor cap on my 1992 300-E. I have 39,000 miles and have noticed a bit of a rough idle. Is there a special way to loosened the spark plug ends off the distributor so I can replace the cap and rotor.
My engine is an M 103 6 cylinder.

Sincerely
Bob Geco