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2000 blazer 4wd

Got this code over a month ago. Started off by replacing the O2 sensors since they looked old. No change. Replaced a lot of bad vacuum tubing. Didn't change anything. Got a cheap but effective smoke machine. Found the upper plenum was leaking at the gasket. Replaced gasket and confirmed the leak was fixed. No change. I have a decent but inexpensive scan tool. Watching the stft and ltft for bank 1 is crazy 50% and 25%. Decided to replace the fuel injection spider. Fixed and ran pretty good for a day. I also tested fuel pressure don't remember the exact psi but it was around 55 as I recall. Code is back and its running like crap at idle. It's new to me so I replaced the plugs and wires early on before this occurred as well as the fuel filter. The cap and rotor looked good (tm) so I didn't replace them yet. Not really sure where to go next. I am going to verify I have spark tomorrow but that's the last thing remotely connected to this I can think of checking.

Please help.
 

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2000 Silverado Z71 4x4 5.3L 460k+ miles w/ GM rebuilt motor and trans
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1,474 Posts
Check your wiring on the O2 sensors for chafing, breaks, corrosion, etc. I just went through 4x O2 sensors and new cats because I misdiagnosed an unplugged sensor and a severed wire on another.

Clean your MAF sensor and the IAC valve.

Check your fuel pressure again.

Hope this helps.
 

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‘01 Silverado 2500HD 8.1/Allison 5sp xcab long bed
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3,881 Posts
Howdy and welcome to the forum, Ned.

Thank you for serving. My brother was on the America before she was retired.
 
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