My 1984 500 SEC just developed a rough idle. Runs perfect other than the idle. I poked around looking for a vacuum leak, no leaks, wires have less than 10,000 mi
I took off the distrib cap and noticed the rotor looks a little burnt and worn. Could this cause a rough idle??
I did a search but no help. Any advise???
The same for my 500 SEL: strong and perfect on the open road but lumpy idle at the traffic lights. I don’t drive it to the city anymore. If no vacuum leaks look for air leaks. It could be the rotor but if bad poor engine performance would be more consistent, as you’d notice problems at highway speeds.
Some owners look for air leaks with a spray can of carb cleaner, others use a spray bottle with water. You know you’ve found the leak when the engine smooths out for a second or tries to stall, depending on which method is used. I don’t care for either method and unless another comes along I’ll give the carb cleaner method a try.
around the injectors, the air distribution hoses (all the black hoses runing to and around your intake manifold). Also spray down below the throttle plate (around where the rubber boot attaches to the lower intake manifold).
I'd also check off the back of your intake manifold (passenger side)..you should have 18-18inches of Steady vacuum.
I know your wires are new but I would check them w/ an Ohm meter anyway..sometimes things go wrong :-P
Thanks for the help I went and changed the cap and rotor.
No Help, was not a bad idea to change anyway, it was time. i feel like an idiot. The culprit was a simple vacuum leak. The vacuum line from the power brake booster simply fell off. I went ahead and changed the rubber mounts for the air cleaner, one was broken.
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