M119 Distributor Cap & Rotor
 

What is the recommended replacement interval for M119 distributor caps and rotors?

Which (if any) ignition system components might fail if the caps and rotors are run for extended periods without change?

I am not aware of any spec, I am going by my experience. I would say 60K mi. Possible symptoms of bad ignition train (coil, distributer, rotor, plug wire, plug) would be misfire and poor operation.

M119 is hard on the caps and rotors... My tech advised 60 - 75K replacement of these parts. It's a reasonably easy DIY task. I think the web site here actually has the procedure on the DIY page. Rough idle and hesitation spells are what I experienced prior to changing out caps and rotors.

I recently replaced them on my 1994 E500 at 75K miles and they were in SORRY shape. I'd recommend 50K. The M119 is notoriously hard on the cap and rotor.

Cheers,
Gerry

Gerry, did you notice any power gains with the new cap/rotor? Mine don't look good - significant corrosion of the cap contacts, lots of green powder. The rotors weren't great but cleaned up ok with sandpaper. I don't have a rough idle or misfire, and top-end power seems OK, but my low-end power may be weak judging by my pathetic 60-foot times. I'd just hate to spend $200 for aftermarket parts ($400 for OE dealer parts!) and have ZERO change in performance...!

:(

When I changed mine I noticed no change in performance at all and my car had 120K miles on it.

It is a common domestic ritual to replace cap,rotor, and plug wires with that uniquely American term a "Tune-up".

Such maintenance is probably valuable with the POS equipment used on domestic iron. MB stuff has no predicted lifespan and I never change such parts as some routine maintenance. Properly tooled technicians can evaluate the components during normal servicing and make specific recommendations.

Defective caps and rotors can cause misfires, hard starting, and in some instances hesitations. A new cap will do nothing to performance unless it is in specific failure.

For those not properly equipted to evaluate the system and who never visit someone who is, they will have to base their maintenance concept on how many wasted dollars they will throw at poor running cars. The look of the inside of a distributor cap and rotor will scare most amateurs, but has very little to do with their capability.

So tell me this
 

Hey Steve,
Got a question for you...
Its 88 deg. here in Texas and I'm crusing the 500E North bound on I45 on a 250 mile 3.5 trip from Houston up to Big D.
I'm stretching the legs out on the ol girl pretty good as the smokey's have apparently taken the morning off. At about the 150 mile mark, I start feeling some intermitent hesitation. Not really hesitation but you know how on a Domestic car, the engine loads up when the AC compressor kicks, well it kinda felt like that only of course I was at 80+ Mph. I was thinking TBA might be headed sout since I'm at ~78K mi. Any way to manually check it. I seem to remember getting similiar hesitation when my TBA went south in 400E.

PS Happy Father's day to ya

Misfire at ultimate load is a posibility for a cap an rotor but so is fuel starvation and plug wires.

If its got a 100k and a hard to diagnose problem such as yours the maintenance concept gains value.

Wiring harness
 

Any thoughts on the dreaded wiring harness. I can find no confirmation that it has beed changed