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Over the past year or so, I've had up and down problems with rough idle/engine misfire under load.

I've replaced the COPs several times. Twice as a complete set (8) and once when a loose wire was found. Every time it fixed my issues.....temporarily. The first time the problem went away for a couple months. When it came back the loose wire was found and the single COP was replaced. This fixed the problem for another couple months.

Last week, after the problem returned, I once again replaced the full set. It was good for 2-3 days then the problem returned. I went out a few minutes ago and started the truck. I popped the hood and pulled each wire harness one at a time to see if I could find one that did not affect the idle.

On one I found a harness that didn't actually "click" back into place.....as in, it wasn't audible. Found another one that didn't seem to affect the idle. After checking all 8, I went around the loop once more to make sure I wasn't crazy. The second time around none of them affected the idle.

Got back into the truck and realized the rough idle was gone. Haven't driven the truck yet (it's late....will find out tomorrow), but it seems like it's fixed again.




Is it possible that I have a bad connection at one of the wiring harnesses?


I never considered this, but after playing with them tonight it seems like one could wiggle loose over time causing an inconsistent spark. Possibly the one that has no audible "snap" back into place....


Any thoughts?

 

Did you wash the engine at all? Is there any moisture getting into the plugs? You could hit the plugs with some white lithium grease maybe. There could be a little grit in the plug or latch (for lack of a better term) preventing it from locking closed.

thats all i can think of.

 

I only wash the engine bay when I'm doing a full detail, but I haven't done that in some time.


I'll check out the connections today at lunch and see if there is anything keeping it from closing. Thanks!

 

let us know what you find.

 

The connections would be the first thing to check. Are you using oem ford coils? The chinese ones off eBay will give you issues. Your problem could also lay in the ECM. You may have a ECM driver that is starting to fail. Most of the time they go to the point the error cannot be repaired without replacing the ECM. I have seen them have a intermittent fail. I would check voltage at each connector. The ECM acts as a switching ground and that controls the coil.

 

I had a similar issue. There is a little built in o-ring type seal inside the connector on the harness side of the connection. What happened on mine was at some point while plugging it in it caught the little seal and tore and pushed it down into the connector. The when I plugged it in a could never get that click sound. It would run fine for a while and then start missing again. I finally pulled them all off and inspected them and found a little piece of this seal down in the connector preventing it from seating completely. It was hard to see as it was just a small piece of red or orange colored rubber down in there. Pulled it out and plugged all back in and no problems since.

 

Didn't have a chance to check it out yesterday---too much going on at work.

I had used Globals the first time I replaced them myself. This last time my mechanic put in OEMs.


That actually sounds promising....I'll make it a point to get out @ lunch today and look into this. Mine does just what yours did....would run fine for a while then start missing. I'm guessing it just wiggles loose.


I'll check it out and report back. Thanks, guys!

 

Well I went and checked them out at lunch. All connections look good and they are all clean (no corrosion).

The one in the rear on the passenger side is a little "wiggly", though. It is a heck of a lot more difficult removing that one than all the others since it's tucked way back in there. Maybe this one is my problem....


For now the truck is driving fine, but if it starts acting up again I'm going to figure out which one it is. Tinker with one connection, drive a bit, see whether or not it fixes the problem, rinse & repeat....

 

My connectors actually broke on almost all mine. The clip in them snapped and fell out. I solved it by putting them on then putting a zip tie around each one for extra security. Easier than replacing 8 plug connectors!