Lean after cam swap

300,000 MILES • 5.3L • V8 • 4WD • AUTOMATIC
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ERIC YODER
  • MEMBER
  • 1 POST
I just swapped out my cam and valve-train components in my heads, and ported and polished my exhaust and intake ports and base tuned. drove fine for a couple days then it didn't start. Engine light started flashing when I did finally get it started so i hurried up and in the laptop and plugged it in. P0300 Multiple/Random misfire. No leaks, had the head off didn't see anything. Shut the injectors off one by one and they all work. And no mix in fluids. Is it possible that when I ported the head I thinned out a port and it crack that way? Any other ideas? I gotta get this thing running again. please help. Thanks in advance. -Eric
Apr 17, 2019 at 6:56 PM
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ASEMASTER6371
  • ✓Experienced Mechanic
  • 52,796 POSTS
Good morning,

I suspect a fuel delivery issue. The 300 code is common for low fuel pressure from a bad fuel pump.

https://www.2carpros.com/articles/repair-lean-mixture-codes-p0171-or-p0174-on-some-manufacturers

Can you check the pressure?

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Roy
Apr 17, 2019 at 8:31 PM
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