the new guy has a question

[beachbums86]

Hey so i'm here to learn as much as I can as a novice mechanic I do okay but I'm stumped on my current project. I've looked around the site a little so far and this looks like the best place to post this question. I've got a 2001 xlt expedition 5.4 a few days ago it started to miss and gave me a p0303 code. so we know we're working with cylinder 3. All the you tube videos I watched and a few other forums said this is typically the coil going bad. So I bought a coil and a plug and went at it. I tested the coil that came out and it was within spec according to my Haynes on primary and secondary resistance. just to be safe I switched it with the #6 coil. Then replaced the plug with a motorcraft platinum plug. I cleared the codes and took it for a test drive and its still doing exactly the same thing and showing the exact same code. A few days before it started to miss I had tried to replace the fuel filter for the third time unsuccessfully. I'm wondering if that had something to do with it? maybe what ever I did messed up the #3 injector? I followed the procedure in the Haynes to relieve the fuel pressure so its not like I did anything out of the ordinary. Any insight would be greatly appreciated.

 

[Bedrck47]

check the wiring connector at the coil clean it and use dielectric grease on the contact areas

Get yourself the ford workshop manual on DVD and burn the Haynes manual

 

[IMINYOURCHAIR]

See if you can swap fuel injectors to see if the problem follows that. If it still has a miss on 3 you should do a compression test. You will need a dull plastic blade to assist removal of o-rings for injectors. The rings should be on the injectors and not left in the rail otherwise you will not be able to re insert the injector in the rail or into the intake manifold I used a small spray bottle of gas to lube the rings before re inserting since it evaporates quickly and cleanly.

 

[beachbums86]

I actually have the hard copy of the ford service manual but I had let a friend borrow it. I also verified battery voltage at the connector to the coil. It seemed fine

 

[beachbums86]

Ok I will try that and see what happens. I did put some Lucas fuel injector cleaner in last night but it's to early to tell if it helped

 

[beachbums86]

Okay so after a little searching I might have found my problem. The Haynes manual I was using stopped at 1999 I think. It said the plug gap should be .054 the other manual I looked at said they changed it after 2000 to be a .045 gap. Would that much of a gap difference cause it to miss and throw a code?

 

[Bedrck47]

copied from the 2001 Ford service manual

also check your owners manual

 

[beachbums86]

Awesome, thanks for looking that up for me. I just got my factory manual back from my friend and it said the same thing. I guess I'm back to looking at the fuel injector.

 

[beachbums86]

update: I think I may have found the problem. I did switch the injector for the number 1 cylinder (because it was the easiest to access) and the problem went from a po303 to a po301, imagine that haha. So I replaced the injector with one from pick n pull and so far no codes. typically it only took a few minutes to throw a code and I just drove it for about 30 minutes with no codes so far. Interesting note though, I did bench test the old injector and it was operational however it seemed to spray about double if not triple what the other injectors I tested were spraying. So my train of thought is this, the small filter inside of the injector may have been torn or something allowing to much fuel to go through and flood the cylinder causing a misfire. I could be wrong but that's what it looks like. Either way I learned a ton through this process and i'm actually kind of glad it happened so that I could learn new things haha.

 

[IMINYOURCHAIR]

yeah, too much fuel will cause a misfire. I have seen a couple of engines with a dead mis and my last call is to move an injector. I usually move the coil or plug wire, then move the plug, then move the injector. you may be able to have the injector cleaned and put back into service but I wouldn't bother. just see if you can get a couple spares and hold onto em.

Glad we could help and I'm happy to see you learned some priceless information!