97 trooper. Is the tube off the ignition coil also called the spark plug boot? There is a small crack on the bottom, would that cause a misfire?

Most likely solution is to replace the s[ark plugs and check the ignition coils boots. The #4 cylinder plug has probably has a carbon track down the side of the porcelain part of the plug which will cause the cylinder to misfire.

Does each cylinder have it's own coil ? (COP ) coil on plug ignition system . Is the PCM - controlling them ? Could have fried driver inside the PCM . How was the spark plug gap ? Worn - this can cause the coil short inside sending 20,000 volts to the PCM driver (transistor)

https://www.youtube.com/watch?v=y4r5OcHN5Lg

CHECK YOUR MAS AIR FLO SENSOR AND THE TUBE CONNECTING THE AIRCLEANER TO THE MOTOR THERE MIGHT BE A LEAK IN THE TUBE CAUSING THIS CONDITION

Misfiring can be cause by ignition coil,spark plugs,wires,engine valve,cylinder compression,
if it's a quad four then crack around the ignition coil. there is 2 coils like 1-4 coil and 2-3 coil
first check spark plug color or foul of gaz
hope it help

Is the porcelain "cracking" or are they getting "carbon-tracked"? (see example photo of carbon-tracked plug below).
It is common for carbon-tracking to occur if your original plugs were carbon-tracked and you replace the plugs without replacing the wires. If the plug is carbon-tracked, the boots on the wires or the coil boots (coil-on-plug ignition) are also carbon-tracked. If you do not replace the wires or the coil boots, the ignition will still misfire by following the carbon-track on the inside of the boot. This will cause your new plugs to also be carbon-tracked within a short period of time (days or weeks).

There is no reason I can think of for the porcelain itself to actually crack other than faulty installation techniques or possibly, cold liquids getting poured on extremely hot plugs.

Faulty EGR valves do not cause "false" misfire codes. An EGR valve that is not closing properly can cause misfires (and misfire codes) but they are REAL misfires when this happens.

To understand this, you need to understand what a misfire is and what kinds of things can cause them. It is a very LONG list and I do not have the time or space to get into all that here.

You will also need to understand this if you are going to properly diagnose your misfire codes without wasting a whole bunch of money on parts that you do not need. MANY things can cause misfires other than spark plugs and ignition coils.

I do not know what EGR code you are getting, but I will tell you that in the 37 years that I have been diagnosing and repairing cars, there has only been once that I can remember that I have ever replaced an EGR valve on a Ford engine because the valve itself was faulty. Most EGR codes on Fords are caused by either clogged-up EGR ports or a bad DPFE sensor. Every so often you will find a bad EGR control solenoid or a broken vacuum line, but it is extremely rare that the EGR valve itself the cause. With the exception of leaking vacuum lines and on certain engines, clogged EGR ports (Like the 6 individual EGR ports in the 4.2L engine), none of these causes for EGR codes will cause any misfires.

Also, most of the time when people pull the trigger on the ignition coils on the 5.4L and 4.6L engines, all the thing really needs is new spark plug boots. They get contaminated with oil and water and can cause carbon-tracking on the spark plugs and/or arcing into the spark plug wells instead of sending the spark through the spark plug. It is pretty much the same thing as having bad spark plug wires on a conventional ignition system. You don't throw the coil and distributor away on a conventional system because it needs new wires. Neither should you replace a coil on a COP ignition system that just needs a boot. Some auto makers do not make the boots available seperate from the coil. Ford at least had the insight to understand that people cannot afford the cost of replacing all of their coils just because the boots are defective.

Hello Mr best wrench.

Certainly could be an ignition coil as it is a common issue.
A small misfire doesn't easily set a code and often a technician will need a scan tool capable of reading the vehicle computer in what Ford calls "mode 6".
This gives live data of each cylinder on a road test.
If it has been a while since the spark plugs were replaced it may be a good place to begin.
Keep in mind that these plugs are difficult to access and proper torquing is essential.
Improper installation can lead to stripped threads very easily on this engine.
Inspecting the boots at the coil for carbon tracks on the inside of the boot often are a clue to misfire.
Also have seen where water intrusion down past the boot and into the spark plug tube causing rust creating misfire as well.
Inspect the tops of the coils for cracks or signs of burn through.
I'd advise also to use Ford original coils as I have had issues with aftermarket suppliers.

There are a few tips for you, I hope it helps.
Thank you for using FixYa.
KL

those are called coil packs or direct ignition modules.one of them isnt working properly.test each one then replace.not to hard of a fix.

spark plug boot.

There are three kinds of gasoline engine misfire scenarios, first there is the "under load" misfire and there is the "at engine idle" misfire, and finally there is misfire continuously. All engine misfires exist because one of three things has occurred. First, a cylinder has lost compression, a cylinder needs a certain amount of compression to operate correctly. Second, the ignition system has failed or is failing intermittently, spark is needed at the time of compression to ignite the fuel air mixture. Third, the fuel air mixture is incorrect, proper mixture is needed for the ignition system to ignite fuel properly. If any of these conditions occur in the engine, the engine will misfire.
1. Low or no compression can be caused by

a. burned or leaking intake or exhaust valves
b. worn or broken piston or piston rings
c. worn out camshaft
d. wrong weight motor oil was installed holding the cam followers from adjusting
e. broken valve spring
f. failed head gasket.
2. Ignition system has failed or is failing
a. spark plug has fouled or is worn out
b. ignition coil
has failed
c. spark plug wires have shorted
e. engine control module coil driver has failed
3. Fuel/Air Mixture is incorrect
a. vacuum leak at the intake manifold
b. fuel injector has failed
c. EGR valve is stuck open
d. mass air flow sensor has failed
e. oxygen sensor has failed
f. air intake boot is cracked

common problems:
1. fuel injector has failed or is failing
2. spark plug wire has shorted
3. spark plug is worn out or is cracked
4. ignition coil has failed is failing

Testing a coil on the car is pretty easy. No special tools are required. Just remember to be careful, the amount of electricity generated by your ignition system can be dangerous. If your coil is already off the car, or if you would like a more specific data-driven test, you can bench test your coil. To set up the test, remove one spark plug wire from its plug, then remove the spark plug using a spark plug socket. Next put the spark plug back into the spark plug wire. Be careful not to let anything drop into the empty spark plug hole -- very bad.