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Discussion Starter · #1 ·
DTC descriptions:
Misfire cylinder #3
Misfire in 1st thousand revolutions
Intake air leak? (Pulled up on my scanner but not his)

5.4L 2 valve 160k

Buddy brought the truck to me today. Truck smelled rich. Looked at the codes, didn’t write them down due to bud light, then took the truck down the dirt road while watching live data. 2 miles from the house the truck lost power (didn’t die) and would back fire (seemed like it at least). Turned the truck off for 10 seconds then back on, truck ran like a beast.

Plugs and coils were replaced 500 miles ago. I’ve got 50 psi after the fuel filter before the regulator and 30 psi on the fuel rail. B1 and B2 STFT were different during the second LD session, but when the truck lost power both banks went from 28 to -20. Tired the starting fluid method but had no sign of a vacuum leak.

So, could it just be the regulator? Or is it more likely a vacuum leak?

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