Greeting to all! I'm posting here because of the commonaliy of Expedition and F-150 engines.

There are so many misfire threads that it's really tough to search for relevant or common symptoms, so I apologize if this has been covered before.

Here's my story:

2002 Expedition with 5.4 Triton. Very high mileage, close to 250K. It's been a great vehicle.

Plugs and coils were replaced about 20K miiles ago. I had hoped that the new coils and plugs would improve the badly degraded fuel economy, but no such luck. I still can't explain why the mileage has dropped from close to 17 MPG (hwy) to around 11 MPG over the last few years, but I'll chalk it up to a very tired engine. Otherwise it's been running great.

A few days ago it started misfiring at cold start and for the first 10 minutes or so of driving. BlueDriver scanner reported pending code for cylinder #2 misfiire. Sometimes solidified to confirmed code, other times started running right before the misfire count got high enough. Replaced #2 coil and plug. Cleared codes.

The problem, exactly as described above moved to cylinder #3. Yes, I checked and reseated the coil and injector connections.

Possibly unrelated - While fumbling around with in the area, I noticed that the rubber "elbow" for the PCV hose was collapsed. There might have been a vacuum leak leading up to these events. In any event, I obviously created or worsened the leak while doing the work on the coil and plug becasue it got LOUD. I temporarily patched it up and vacuum is good now. Still throwing the #3 misfire code.

Not much to go on, but the coil, injector, and control seem to be right for #2 now, and they were right for #3 until the above operation. I observed this for several days, and the only reported misfire until now was #2.

I'd welcome any ideas or wild theories.

Thanks,
Tom

 

It could be the 2-wire connectors going to the coils. If the contacts are not clean then unplugging them and plugging them back in might scratch the contacts just enough to make better contact for awhile.

 

Your not taking a close enough look at the overall live engine data if your Scanner can do it.
What are the codes you see. 30x or 35x codes? Makes a difference as to the causes of misfires.
Have you looked at the misfire monitors for each cylinder? They are in mode 6, test 53. They will ID cylinders with high counts.
Have you looked at the long term fuel table readings both banks for their shift percentage? BIG affect on fuel mileage.
Until you get a handle on these items, your just floating around on the issues.
Good luck.

 

Looks like Bluegrass7 is on top of it but i have dealt with issues of misfires also. If the misfires are moving around, check coilpacks. Ohms are easy to check and will tell you if they are good. I have seen coilpacks go bad after 100 miles and new ones faulty. Just saying.. We chased a misfire one time with the VCMll and went back to old school with the meter..Found bad coilpack..Sometimes all that data can confuse us old guys if not used to looking at it.