Do you know the useful life of ignition coil?

I am consuming fuel in reasonable amounts, acceleration is ok, no misfire under load etc.

but when it comes to idling, i can feel a cylinder misfires periodically, or it feels so. 1 missfire per 20 secons.

distributor cap, rotor, wires are mopar and brand new. car is on 92000 miles. 1997 make ZJ. spark plugs are champion and suggested models in users manual. driving this car for 1 year.

Three things i can think about are,

1. distorted,burned etc exhaust valve. may be carbon deposits.
2. ignition coil
3. idle controller
plus: worn-thorn engine mounts which are not able to absorb vibrations.

i want to ask if you have 4.0 engine which idles silk smooth? or is it normal for these machines?

 

What is the life of a coil? That is impossible to predict. I had one go bad on an 80,000 mile engine in the '97. My '98 has 174,000 now and it appears to be the original coil. I'm the second owner and am not completely positive. The previous engine in my '97 had over 230,000 on the original coil. I don't think that this is your problem.

My '97 never idled completely smoothly. My '98 idles a bit better, but not perfectly. Straight 6 cylinder engines have had a reputation for less than perfect idling. I've seen this with Ford, Chevy and others over the years. Unless you have other performance issues, I wouldn't be too concerned about this.

 

thank you for answer. i have no performace issues. it seems, it is better not to concern too much.

 

Mine has done that for the 3.5 years I've had it. I got it with 150K and now have 193K on it and I've tried everything shy of a full rebuild with no change. Mine knocks a little and idles a little rough, especially when cold. I've done the valve cover clean and ccv system replacement, new plugs wires rotor, tore apart the throttle body and cleaned it shiny, replaced most sensors and still the same. No real performance issues other than I've convinced myself I can get 25mpg on the highway if I try hard enough but haven't found the trick yet.

A lot of people say different kinds of spark plugs make a difference in the idle quality and throttle response, but I haven't tried enough different kinds to know if that's true or not.

I wouldn't worry if I were you! (mebbe just check the plug connections and gaps though, just cuz I'm paranoid)

 

Is the computer putting out any codes?????? Every 4.0 I have had, (5 of them), ran like the tractor motor it is. They all had a lopey idle, or what seems like an occasional miss. All did this from the day I got them, 2 were new off the lot. All of them knocked and ticked after a couple years of use. Seafoam will help with carbon build-up.

 

even my spark plugs are on 7000 miles only, i decided to check them. when i removed all, all colors were same, signs of healthy engine but, number 1 had shorter gap than others, may be half of normal gap. since ours is bi fuel setup with propane and it is more prone to miss on LPG, gap makes a big role. before installing new ones, i re adjusted gaps for LPG and now it idles much better.

but since you all reported that it is usual on all 4 liters, i will not worry.
thank you for information.