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56.3 runs rough when cold & WOT
My '99 5.3 pops and farts when cold and WOT with a load. Starts fine and runs well when warm. Runs fine cold too if I don't open the throttle too far. Has 304k miles and is mostly original. The intake gasket was replaced at 100k when I replaced a noisy lifter. I also replaced the fuel press reg at 200k. Everything else is original including the O2 sensors. Any ideas? O2 sensors? Injectors? EGR? I just replaced the plugs, wires and fuel filter as they had 120k on them, but it didn't help. Thanks!
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72 GMC Sierra Grande SWB 402 BB A/C
(Owned it since 1973)
99 Silverado 1500 LT with 315K miles
(RIP)
2012 GMC Sierra SLT
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