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Hello all. First time posting.
2001 Suburban 1500 5.3 280k miles.

It starts and idles just fine. I can accelerate from 0 to whatever with no problems. But there is a lot of hesitation and stumbling on reacceleration after driving 40+ mph. I feel it a lot in stop and go traffic. For example, I'll be going 60 mph, hit the brakes, and start accelerating again with light gas pressure and it will hesitate like crazy. The CEL will start blinking. It'll come out of it if I really get on the gas.

The main codes I get are p0401 and p0405. I replaced the egr valve with a new aftermarket one. I fed speedometer cable down the ports with a drill to look for blockages. I sprayed carb cleaner all over egr tubes and connections with engine on; no noticeable vacuum leak. I took off the throttle body and cleaned it. Also checked the egr entry into the intake. The weird part is that the same symptoms will happen even if I unplug the egr which leads me to believe that egr is not the real issue.

I will say I'm overdue for spark plugs and wires and its on my to do list but could that cause this problem?

Recent mechanical work (past 2 years):
Catalytic converter
Fuel pump pump and filter
Radiator

Any thoughts or a direction I should be going.

Thanks.
 

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2000 Silverado Z71 4x4 5.3L 460k+ miles w/ GM rebuilt motor and trans
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555 Posts
I would check your fuel pressure to ensure your fuel pump is performing adequately. I have replaced multiple and the replacements were just as bad as the original...
 

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No spark plugs change for 280k miles? Way overdue.
I am on my 3rd set on spark plugs and 2nd on wires.
Runs smooth and pulls a 5k lb camper.
At night, spray some water mist by the spark plugs wires and look for a light show.
 
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