Hi all,

I've scoured the threads for a good portion of the evening looking in to this issue.

This started awhile ago, a misfire on #7 which was finally caught by my mechanics scanner after the engine light locked in. He replaced the coil (easy job I know, but didn't have time when this happened). The issue continued. So once I was freed up I continued with the dreaded spark plug replacement. My truck only had 68k and even with following advice from various forums and YouTube videos I still broke 3. Not a big deal with the lisle tool.

Anyway, job done, take it out and I get the light flashing (by this time I purchased my own scanner) and I could see that it misfired on #7 again. After driving it today, it idles very smooth and most of the time runs good. However, if I load the engine around that special speed of 40-55 mph it likes to misfire. My scanner can count the number of misfires and I got a total of 198 in a 25 mile drive. The number of misfires reduced to about as I drove it more during the day. However, I haven't figured out how to display, if possible, which cylinder is misfiring since it doesn't throw a code when it misfires.

Also while driving, I was monitoring fuel rail pressure and it always around 39 psi.

I picked up an injector. Should I just go ahead and replace it?

Is there a way to diagnose the injectors and could using a multimeter? I've thought of spark testers and noid light (for testing pulse to injector) but id rather not go there yet.

With all the threads, is a there a more reasonable solution that has been arrived at other than a mass replacement of expensive parts?

Thanks for any and all help and suggestions.

 

Just went for a drive after replacing my fuel filter. No change for the better. Kicked it down from a rolling start and it misfired quite a bit to the point I could get a code while the CEL was flashing. Same P0307 number 7 misfire. I think I'll first try swapping coils to 5 or 6 and see if it moves. It's hard to believe such a coincidence since #7 is the only brand new coil. If that doesn't work I'll go for the injector on that cylinder and probably clean the others while I have the whole fuel rail off. Blah.

 

Nothin? Hmm

I swapped out coils with another cylinder. Misfired again on the same #7. I'm getting pretty good at causing it to store a code. Drive about 45-48 mph and slowly accelerate up a hill. That's when it really likes to buck around.

 

For the record,

I removed my injectors this evening. I hooked up a quick test to see if any were leaking. Also I used the same test rig to clean them out. It's just a 12v battery, some leads and a switch or button so you can cycle the injector while pressurizing with a syringe of carb cleaner. Look it up. YouTube is pretty great.

I found my #7 injector to spray regardless of switch position. This is bad but good. I finally found something.

Picking up an o-ring kit tomorrow to reinstall the 7 old and 1 new properly. Hopefully then I can write a final entry to my diary for this chapter in my life.

Mmm beer.

 

What year is your truck? Ford has an extended warranty on the injectors because they get stuck open.

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It's a 2006. I've seen that customer satisfaction program mentioned in the forums. My truck was manufactured 9/05 but the document states 2005 model year trucks.

I have a new injector but now I'm stumped by the o rings on the injectors. Rail side are blue, port side are green. I removed them from the broken injector and they are definitely different in size. However, this could be from the different conditions they have been exposed to. But I doubt that. The rail side o rings are thicker in all dimensions. Ford part number cm-4717 is a kit of 10 (why 10? In case you jack 2 up when installing?) o rings but who knows if that is 5 for top and 5 for bottom. The parts fiche actually calls out the same part number for the top and bottom o rings.

Any idea?

 

http://www.fordparts.com/Commerce/Pa...rd&model=F-150

 

They are different because the top o ring is exposed to fuel pressure, while the bottom is not. I would guess they are different sizes so that you don't mix them up. Apply clean engine oil to them to prevent damage when you install them.

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Thanks for the response.

That was the same conclusion I arrived at. I bought new ones for the top and replaced those. I cleaned up the bottom ones and lubed them. It's really odd that you can't buy replacement o-rings for the bottom. They still looked to be in good shape.

I'm happy to report that the injector was, in fact, the culprit. Although this whole thing was a huge PITA, I really did learn a lot. I bought a scan tool and that helped me tremendously with diagnosing. Fuel trims, O2 sensor data and the like. Hopefully it holds together for awhile.

What else can I expect to replace on this truck? I've done the spark plugs from hell, bad injector, and replacing the IWEs and solenoid for the 4x4.