I apologize if Im posting in the wrong place,This is my first Ford ...So I finally did a tune-up on my wifes 2002 Excursion V10 Gas,Replaced all the plugs had all the COP checked,after doing all that I had a miss and it never gave a check engine light,Took it had it scanned and said misfire in cylinder one,Checked the Plug and COP,Replaced the COP with an Accel aftermarket one,and it still is missing,I even took it back and exchanged it for another one and still misses...Im at a lost if anyone could chime in here and point me in a direction or tell me what to check I would gladly appreciate it... John

 

Hi John,

There are lots of things that can cause a misfire; of course the COPs are a common culprit. But there are other things as well...

So the misfire wasn't present before your tuneup? Have you checked the gap on the offending plug? Is it misfiring constantly, or only under certain circumstances?

 

Change out that plug, could be defective... That is if you did not have the misfire before you started.

 

Thanks to you both for the reply Im pretty Mechanical but never have I worked on a ford..I apologize I did have the misfire before changing out the plugs and inspecting the boots,Put new COP on still had misfire went to Auto Zone and had is scanned and states p0301....Thanks

 

Okay then, we have something more to work on.

If the misfire is constant there are some things you can try. By replacing the plugs you have ruled one thing out. Next step is to run the engine while unplugging the COPs one at a time. For each one you unplug you should hear the engine run worse, when you get to one that doesn't change you have found your bad cylinder.

At that point you have to start troubleshooting. First step I would recommend is taking the COP from your bad cylinder and swapping it with another cylinder. Then unplug each to see if the dead cylinder moved or stayed the same with the different COP. Obviously if it stays the same then the COP isn't the culprit. Since the plugs are new we can assume those aren't the problem as well.

Check the injector wire harness to make sure it's tight. Next put an ohmmeter on the injector and measure resistance; if it's not between 12-18 ohms then you have a bad injector. If the injector tests fine then I would move on to engine compression.

Get an engine compression test kit and test each of your 10 cylinders. Is the dead cylinder more than a few PSI off from the others? If it is then you know compression is your problem. Now to get more specific, squirt some oil down the spark plug hole and retest. If you're lucky compression will remain the same and you will have a problem with your valves or seals. If you're unlucky you will see increased compression after adding oil to the cylinder and it's REBUILD TIME!

 

You never mentioned boots.

 

All boots checked out fine...I went back out ohm the Injector and got 18,Pulled the connector on the #1 coil no change,Pulled the connector on the one next to it could hear engine to start running rough plugged it back in and ran smooth ...So now its a Compression problem?..

 

Now wait a minute...you skipped a bunch of steps!

Swap the COP and see what happens. You did, however, verify the bad cylinder. And my boots looked just great as well, but a miss mysteriously cleared up after I replaced all the boots anyway. It doesn't take a visible crack to short to ground, so I would replace them anyway. Of course swapping the COP will localize this is if it's your issue because the suspect boot is attached to the suspect COP.

I do NOT think you have a bad engine. Ignition issues are relatively common, and internal engine damage is extremely rare.

 

You say the boots checked out fine but you didn't say you replaced them. All it takes is one with a crack in it with moisture/grime inside the crack so small you wouldn't see it.

 

So I went out pulled the spark plug cleaned regapped closer to .54 swapped the New Accel COP with the another existing COP unplugged each one at a time saw a difference in each one except cylinder #1 when I unplugged it there was a very small difference..It did Idle somewhat better though... Could using a HI performance Accel COP with the stock ones be causing the problem ?...I cant afford a Rebuild with the Holidays right around the corner

 

watch that and his other videos. It will give you other things to look at.

 

OEM cops are the preferred thing to use.
Try swapping cop and boots.
Try pulling the injector connector.
How many miles on this animal?

 

I doubt if you will have the rebuild anything. I would swap everything on that hole with another one or put all new stuff on # 1 since you have it narrowed to that hole. (plug, boot, and cop). If you are sure it was idling better you are going in the right direction. Still no comment on new boots and you need to replace all of them before I can help with it.

 

Please forgive my ignorance but what am I looking for when I pull the injector connector when the Ex is running?..Im new to Fords but after this I should be pretty knowledable haha

 

EXv10 the only new boot is on the new Accel COP I replaced on the #1cylinder...It was late when I finished messing with it last night and it idle better after regapping the plug and putting a small amount dialetic grease on the top of the plug in the garage and didnt miss all that bad in reverse and Drive with foot on brake..Will know more when I dirve it today I will let everyone know..Wifey keeps saying put it in Ford Stealership trying to keep from doing that she must think we are made of money !!!