Pretty straightforward question here...

When is the "correct" (or appropriate) time to R&R distributor cap, rotor, and wires? Do you wait until problems crop-up, or do you replace these items to prevent said problems?

As an aside, are there ways to prolong the life of these parts (i.e. cleaning or other normal maintenance procedures?)

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Eric

1991 560SEL-Euro (214,000 miles)
1989 420SEL (Retired from daily use at 325,000 miles; Use as donor vehicle)

If the cap has cracks obviously change it, take a look inside the cap is there a clean surface on the terminals that contact the rotor ? then clean the cap and rotor and leave alone, if there is corrosion then it would be a good idea to change out, unless the middle contact to the coil breaks the chances of you being stranded are slim, it would just run crummy, I would change out the spark plugs, spark plug wires, cap and rotor and that should keep things just fine for quite some time, there is a recommended interval to change these but I do not know exactly what that time period is.

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Jerry

2004 SL500 Black 55K Miles
2002 s500 Black 90K Miles
1986 300E Gold 233K Miles
1966 Twin Cessna 320D
1989 Jeep Cherokee 233K Miles
1994 Ford Van E150 399K Miles

I'm not aware of any specific change interval published by Mercedes.

You should probably inspect and clean the cap/rotor and check plug wire resistance at 60K and then every 15K interval after that or at least every 30K, which is the spark plug change interval.

Engine misfires or busting an emission test with very high HC (well over the limit) with acceptable CO indicates misfires, which can be caused by deteriorated secondary ignition system components.

Duke

Thank you gentlemen!

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Eric

1991 560SEL-Euro (214,000 miles)
1989 420SEL (Retired from daily use at 325,000 miles; Use as donor vehicle)