560 plug wires

[yeldogt]

Quick question -- over the years we have had quite a few 560 motors in the family -- all have had rough idle problem and slight engine miss problems over the years -- not major -- just a pain.

All were finally found to be plug caps usually and sometimes it was the wires - in general cheap fixes. But still a pain.

I was wondering why -- I do not see this as much on other motors -- Does the 560 run hotter? anyone have an idea?

This type of problem is hard to pinpoint without the proper scope

[BobK]

I expect you are right on the money about the heat. Underhood temps seem quite high to me on my '87 560SEL. Think I may need a set on mine and on wife's SL. I have had similar problems with my 7.4L Suburban. They run real hot (195 t-stat from factory) and tend to use up wires. Gets even worse if you tow since temps go even higher plus need for max spark under high load.

[yeldogt]

I posted this only because many years ago a tech at the local dealer -- said to first suspect the wires/plug ends on this motor.

I ran into this last year again on the 88 (last 560 still around) young tech said he thought it was the injectors ($$) sure enough it was a plug wire or end -- I can not remember.

I wanted to post this because it can be a very strange problem -- years ago wet weather would set them off on most cars, but I have had the problem come and go and have the motor run great in wet weather and bad in dry. Only to have a plug/ wire be the cause!!

With the age at thgis point all will suffer this problem -- I have never had a problem with a rotor , cap, or coil on these cars.

In fact I have never replaced any injectors on any!

[BobK]

I did just replace the injectors on mine a few months back. Car had a terrible hot start problem. Ran rich as could be if say you stopped for 10 minutes at a store and came out to start it. Only way to start was to FLOOR it till it hit about 3k rpm then idle it at about 2k for a couple of minutes. Else it would idle at 500 and pour black smoke till it would slowly increase revs and clear its throat, so to speak. New injectors instantly solved the problem and seemed to make it run a bit smoother. Best guess is that a couple of injectors were sticking open and flooding a cyclinder or two. Not a cheap fix. About $500 by the time you buy all the other parts like rubber hoses that are now petrified. Once again, I think the victim of high heat.