On and off miss. Codes for ignition coils

Jkude11 · Oct 9, 2022

Hello all. I'm new to this but after a year and a ton of money I'm stumped. I have a 2004 f 150 fx4 5.4v I have had it fully rebuilt and it started missing. Not all the time. It will run fine for 5 minutes and it's like a on and off switch is turned. It just starts missing. 2 mins later runs fine. 4 mins later starts missing again. I've replaced coils with a 400 dollar set. Vvt solenoids. Pcm. Plugs. Expensive ones. Check ground wires. It throws codes for ignition coil primary fault. Like 3 different coils. Coil a, d,f . If I clear it with my tuner it throws different coils like b,c and e. I'm frustrated...any ideas?

FTZ HAIC · Oct 10, 2022

For future reference, only use Motorcraft coils. I have found after market coils to be far less reliable and swapped them out for Motorcraft countless times back when I was in the tuning business. Accel, Granatelli, etc.... none of them lasted long.

It's helpful if you post the exact codes, since there are several sets of codes numbered 0-8 and 1-8. Since you labeled them "A", "B" instead of cylinder number, I'm going to assume PO35x codes. This usually the PCM coil driver might be shorted either to ground, or power. And if driven long enough like this, it'll fry the driver in the PCM.

I could list some simple tests, like 12v at each coil with ignition at each on but not started - but this guide is one I've bookmarked because it's comprehensive:
https://easyautodiagnostics.com/ford/4.6L-5.4L/how-to-test-the-cop-coils-1

On and off miss. Codes for ignition coils

Jkude11

FTZ HAIC Staff Member Oregon Chapter Founding Member

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