Cylinder 1 Misfire. NOT plug,coil,or injector. Help

[Drae]

I had a 2003 with the 5.4 and a similar problem. Dealer ended up replacing the harness for the #1 plug and that fixed it.

My wife's 03 5.4 had the same issue where one of the pins became loose inside the ignition coil harness. I replaced it with one from O'Reillys. It was a ***** to do considering it wss cylinder 4 but it definitely cured that hiccup.

 

[BrinkExpo]

Did you check harness for #1 fuel injector? You need to be sure theirs power going to that injector. Putting sea foam, and all the other miracle fixes, is not going to get #1 bank right again. Before you dive into the valve train, make sure all with the fuel side, as well as the ignition side is sound. You said the dealer swapped out coil, and spark plug, and problem wasn't corrected. Depending on your patience and skill level, you can proceed with the members help, or you may choose to have a shop complete. We've all done it. Sometimes our time, and sanity outweigh frustration!

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Yes I replaced the plug, coil, and injector.

How do you check harness for #1 injector to make sure it is good?

 

[1955moose]

You can borrow/ buy a set of noid lights made for Ford, or use a volt/ohmmeter and check for voltage at plug. Noid lights are a small plug with a light in them that plugs into each part of harness. You can find procedure online.

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[1955moose]

Theirs a great article I just read on how to test your injectors on 4.6/5.4 with noid. Light. Might want to read it.

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[BrinkExpo]

When I replaced the injector it wasn’t fully seated and it definitely spit fuel out of there. I got it seated fully now and it doesn’t leak.

Is it still a good idea to check the harness for that injector?

 

[1955moose]

Depends, how's it running now?

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[BrinkExpo]

Depends, how's it running now?

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The same. It starts great, idles great, and drives great. The misfire only happens under hard acceleration at 3,000 RPM and above and it is very noticeable.

 

[1955moose]

Your describing an electrical issue now. You stated earlier that the dealer said nothing was wrong with plug, coil, etc, and even swapped it around. If your getting a hard miss that progresses with speed, that has a hard jerking feeling, like a light switch going on/off that's usually secondary ignition, Ie coil/ boot/ spark plug. Fuel symptoms are usually a little softer feeling. I'd still isolate all fuel delivery problems, to be sure. I know this will sound a little nuts, but you also stated dealer said compression was good, how did they test it? Let us know. Any one else want to join the party? What am I missing? Fuel, spark, compression?


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[1955moose]

Check the injector plug for voltage, and pulse, just to rule out. If your 100 percent sure that your spark plug and coil are sound, and fuel is also, their may be an issue with the engine itself. Possibly a bad valve on that cylinder. Let us know.

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[BrinkExpo]

Dealer said relative compression was good when he hooked the computer up but could still have broken valve spring that’s doesn’t allow it to close at higher rpm.

What is the best way to check valve spring?