rough idle -- explained?

hello, would any of you experts be able to post a Web site (or suggest a source) that explains *rough idle* (generally)
(what is mechanically / technically occurring)
thank you in advance!

Yes, just use a laundry spray bottle on mist with water in it and mist the whole works.

Ok, you have lots of 'issues' from your previous posts, right?.

Low ground power to the body tub can and will cause a lot of the symptoms and an almost dead one will make a rough idle for sure.

That means bad connections on the main cables.

The main battery cables have two ends that can go ratty and need a clean.

The engine has a mesh ground strap likely to the firewall or across an engine mount, that can go ratty too.

Some batteries have a second ground to the fender or firewall, a dirty connection there will cause your symptoms too.

That's a tough one.

A rough idle can be caused by dozens of things, from a fuel or air filter getting plugged to a bad spark plug wire, dirty distributor cap, bad spark plug, to some emissions component with a dirty filter or worn out....
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's

thank you, Mike so spray each wire from distributor cap to where it goes into the engine i assume...
thanks again sincerely [...below -- if time...]

the distributor cap and ignition rotor were recently replaced and prior to that it idled roughly so the replacement had no effect on the idle

just wonder: where i live a favorite *diagnosis* is the car's "old age" (it IS
1989) however has 70,000 miles (141,000 km) on it (only) and wasn't sitting around for any length of time and has many "lucid" <sorry> intervals..

thank you, Mike do all of the above causes result in the SAME *effect* (bad example but...
a sore throat can be caused be many things (yelling, infection, trauma, allergy etc) but the end result is <superficially> the same -- is a rough idle basically due to the same thing <what?> (despite the many causes)?
not very clear
thanks in advance!

"Tanya" wrote

Oh, so you just want to hear that one or more cylinders not firing correctly, either constantly or intermittently, will result in uneven power pulses from those cylinders, causing a general "roughness"?

thank you for replying (assuming that the above is the end result of the various causes (for example an electrical problem would cause cylinder roughness?)

Yes, pretty much all end up sounding the same.

If you work on one type of engine all the time, you get to know what is the most 'usual' cause for a rough idle and check that first.

For instance on the Jeep engines I play with, the 'usual' cause for a rough idle is a blocked idle tube in the carb. On the other type of
Jeep engine (fuel injection) I work on, the 'usual' cause is a dirty plug on the TPS. (throttle position sensor)

Second 'usual' thing is a dirty distributor cap and rotor, especially on electronic ignitions, so I check that next. (Folks tend to forget about the cap and rotor because there are no points inside it to change during a tune up.)

Then I think of leaky spark plug wires so I open the hood in a darkened place or cover it up so it is fairly dark and spray a mist of water on it when it is running, if wires are leaking voltage the water mist will show it up fast.