I'm new here but I've used this forum before for countless problems. I haven't seen a thread about this one yet

So my truck has over 245k on it. It has a misfire code for cylinder 4. I've replaced the intake manifold because the old one cracked at the water crossover. I've done Accel coils and motorcraft platinum plugs. I've cleaned the injectors too. And for about 400 miles it ran fine but then the misfire came back. I haven't done a compression check yet. I don't really have the time to yet. What else could be going on? Anyone know anything about the ignition system checks?

Any help is appreciated

 

When you take out the #4 spark plug and coil to do a compression test, swap those two items into two different cylinders. That way you can see if the code moves or stays. If it moves then you know it's the coil or plug, if it stays and compression was good then it's likely the fuel injector or wiring.

 

I've moved the plug and coil around. I haven't done a compression test yet. Do you know of any good ones. Since the spark plug threads are so far down in the head

 

May be irrelevant, but, mine was doing the same thing. I replaced all 8 coils. It ran fine for a few days then developed the miss. Mine was 3 and 4. Swapped coils around but the miss remained. Had someone tell me to use dielectric grease in the boots. Did that, and the miss is gone. At least for now. Hasn't missed in 2 days.

 

Diagnostics is the key.
It is a hassle and costly to move parts and replace hoping to get lucky and even miss the results.
Get a Scanner that can look at data.
Look at mode 6, test 53 at the misfire monitors for each cylinder.
See which ones have a high misfire count and replace the coil and boot.
As a hint from experience, I suspect ACCELL coils. The quality from China is not good. You don't know if you got one or more faulty out of the box.
Mode 6 look is the only correct way. This is what Scanners are made for.
Use Motorcraft OEM coils.
Once you get these looked at and cleared then look at other issues that may be present.
Good luck.

 

They're all pretty much the same. You might be able to rent one from a local auto parts store so it doesn't cost you anything.