1999 Ford F150 V8 4.6L Misfiring: P0306, P0308 & Bank 2 Lean Code - How to Diagnose and Fix

You've used multiple types of plugs — Motocraft, Autolite Iridium XP, and now Autolite Platinum. Are these the correct or recommended parts for your engine? Also, could you confirm which specific 'lean' code you're seeing (e.g., P0171)? There's some confusion around cylinder numbering — cylinders 4, 6, and 8 are on opposite sides of the engine. Could you clarify where exactly #6 and #8 are located? Please check for spark at each plug: is it present? What color and condition do they show (wet/dry, black/tan)? Also verify injector connector connections and use a noid light to confirm injector pulsing.

Thanks for the response, Kev2. Unfortunately, I no longer see the lean code — it may have cleared after some driving or due to sensor reset. I can confirm that I've tried Motocraft, then Autolite Iridium XP, and now Autolite Platinum plugs. All are OEM-style parts, though not necessarily factory originals. I do get spark at cylinders #6 and #8. The plugs appear dry with a light grey color — no visible wear on the tips. I unplugged injectors for cylinders 4, 6, and 8 one at a time. When I removed cylinder 4 alone, there was a noticeable change in misfire behavior. The same pattern occurred when I disconnected both #6 and #8 simultaneously. I'll be purchasing a noid light this morning to check injector pulsing.

Let's clarify the cylinder layout first — cylinders 4, 6, and 8 are on opposite sides of the engine. This is important because confusion about firing order or physical location can lead to incorrect diagnosis. Could you confirm where exactly cylinders #6 and #8 are located? For example, driver’s side near the firewall?

Apologies — I meant driver's side. Cylinders #6, #7, and #8 are positioned closest to the firewall on that side.

Got it — we're now aligned on cylinder layout. Spark is confirmed at cylinders #6 and #8 — good. Next step: verify injector pulsing using a noid light. While you’re getting the noid light, consider adding a bottle of Techron or Seafoam fuel cleaner to address potential fuel injector buildup or gumming issues. Ideally, an OBD2 scanner would help monitor real-time data like MAP pressure, misfire counts, and other parameters. But since a scanner costs $299, we’ll work through basic checks step by step — slow and steady is best.

I just picked up a noid light and tested cylinders #6, #7, and #8. All showed pulsing — though cylinder #8 was slightly dimmer at idle, it still pulsed consistently. I’ve also added Seafoam fuel cleaner to the tank, but only drove about 2 miles before returning home. I plan to drive approximately 35 miles tomorrow morning and will report any noticeable improvement in performance or code behavior.