Ok so... not really sure where to start on this one. I have an 03 Expedition, 5.4L Triton FX4. Well, it had a miss and the SES light kicked on. I had it read and it said it was an open circuit on the #2 fuel injector. However it no longer misses but I have to clear the code.

While it was missing the one day really bad it downshifted pretty hard to get up a hill, and then it had no O/D when it had the chance. Just revved like it was in neutral. So I turned off the O/D with the lil fancy button and it ran fine, as it should. Ok.. so I did all the homework on this problem and came to the conclusion that either the E-Clip or the snap ring had broken. I got all the gaskets and the ring, tore it apart... and nothing. Everything was intact. I tore the valve body apart anyways to make sure all the pathways were clear and the valves were able to slide correctly. everything looked good so I put it back together and filled her up with fluid. Mercon V of course. It still wouldnt kick into O/D tho.

We took the truck up to WI last weekend and just ate the low MPG's (about 180 miles). Now, the other night I had forgotten to kick the O/D off... but didnt notice it rev up like it was doing. Now just about 30 mins ago I drove it for a while with the O/D turned on and it WORKED PERFECTLY. So I guess my question is... is there some kind of built in safety that could tell the tranny its not safe to be in O/D? And could it somehow reset and work perfectly again? Or did me changing all the fluids and making sure its all tightened somehow fix it perhaps?

I'm completely baffled as to WHY it would not work... then all of a sudden work again out of the blue a week after I had worked on it. Any suggestions or ideas would be greatly appreciated.. told my wife it works again (its her car) but dont want her to get too excited in case it just stops again. thanks

 

I don't know if this is/was your problem, but a coil going bad could be the initial cause of the miss while the PCM will disable the fuel injector to save the converter from overheating and cooking the inside.
You didn't state how many miles were on the vehicle and/or if any coils have been replaced, but it is a point to consider. Those coils can send a voltage spike into the system and really mess things up.

 

It has about 98k on it. I suppose what ur saying could make perfect sense for the miss/SES light being on. My main concern was the transmission. I'm not sure if any of the coils have been replaced, I'd have to look into it further. I just bought it about 2k miles ago. My initial thought with the miss was coil as well. But the overdrive not working, then not responding to my workin on it, then suddenly working again was my concern. Unless this is what you were referring to when you said converter. Thanks

 

Voltage spikes can be very destructive to the electronics in the vehicle and can cause some weird problems. It might be a good idea to check all the fuse connections since there are two fuses that are involved with the OD switch and system.
Also, while you are under the hood,check the heavy gauge wire from the alt to the batt they have a junction on the driver's side fender well I believe, that likes to develop corrosion. Make sure its clean and making good contact.