My neighbor's truck, 2006 Lariat, is misfiring on hills and rapid acceleration. Pretty sure it's a coil. I unplugged the coils one at a time. On all but one, the idle got noticeably rougher. One one, there was almost no change when it was unplugged, so at this point, I'm assuming that it's the one. Odd thing is that with all the misfires during driving, the engine light never came on. When I did the tests unplugging the coils, then it did. I guess the ECU needs to have a certain number of sequential misfires before it posts a code. So is this a valid diagnosis?

I see there are a lot of non OEM alternatives ranging in price from $5 to $40. Are there any recommended brands or brands to steer clear of?

Also, I had trouble getting one of the connectors back on. When I looked into the connector, the rubber seal was torn and out of place. I was able to get most of it out, but a small piece worked it's way to the bottom making it very difficult to seat. I checked the other connectors and a few are completely missing the seal. How important is this seal and is it available as a replacement item? Or do you need to change the entire connector shell? Looks like some sort of special extraction tool would be needed.

TIA
Rob

 

If you or your neighbor, can afford it , motorcraft is the best solution.

 

Not really a good way to diagnose a misfire issue.
No code, you need to look at it with a Scanner, at the misfire monitors to see which cylinder has the issue, then address it.
Otherwise it's just guessing.
The more you work on it the greater chance you have to get deeper into trouble, then it's your baby to fix.
Good luck.

 

I bought Motorcraft coils on Amazon for about $40 each. I guess it's pretty common for no codes to be set from this type of misfire. I never really understood when I was looking at the scanner why I would only see one cylinder misfiring at a time. I'd fix that one and another would appear. Must be the way the algorithm works. The scanner is really helpful, though. It also allowed me to troubleshoot an O2 sensor that was completely unresponsive, but it seems that the better ones do cost more $$$.

Dave

 

I'm currently having a similar issue with my F250 5.4L. It seems that if I'm going uphill and light on the throttle it will misfire but if i get the rpm's up it wont misfire or so it doesn't seem like it is. I changed out the spark plugs last week and seemed like that fixed the problem then i noticed it again three days later. I bought the truck from my father-in-law three weeks ago. I'm assuming that i can hook up determinator and drive around and hopefully the scanner will catch what is going on. This weekend I'm going to tackle changing the knock sensor that is bad.

any suggestions would be appreciative. My appoligies for hijacking your post

Thanks,

 

Use a Scanner to look at live stored data in mode 6, test 53.
Accessing this data shows the misfire counts for each cylinder.
The one with the high counts is the offending coil/cylinder.
Good luck.

 

Something that nobody tells you is that not all scanners call it mode 6 data. I didn't think I was in the right place on my scanner because it never said mode 6 anywhere, but I did get the $53 test. On the Innova, it's called Special Test -> Non-Continuous Test.

Dave

 

For anyone wanting a good layman's term explanation of what causes the shudder/flutter at speeds associated with a coil dying, check this thread: https://www.ford-trucks.com/forums/1...45-50-mph.html

Specifically see post #138 and 177 by Bluegrass7. If you have a little bit of understanding on how an engine functions, his explanation will make it crystal clear. I know this topic comes up a lot, and the thread linked to above, has a lot of good info in it. Bluegrass7 has this stuff down to a science, and his knowledge is invaluable. Good luck.

Jim