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Discussion Starter #1
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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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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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...
I(repair shop) had to replace one on my 2003 suburban at 80,000 in the middle of a trip. $1800 bucks and did not help it had a full tank. Acting up now 195000 but I know how to drop a tank but no time and truck driven locally. If it does not start once in a blue moon do the punch the tank and wakes up. I can see the hesitation upon start sometimes but engine and car drives fine. Too bad no access from inside truck to remove. Best aftermarket pump or none out there as you kind of implied.
 

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Discussion Starter #6
Update. I checked the fuel system and it looked good. Changed out plugs and wires and the hesitation/stumbling is gone. Thanks for the help. Lesson learned.

Moving on to the next issue. When I start up the truck in the morning or after its been sitting awhile, it makes a groaning noise. It seems like it's coming from the rear. It goes away after driving for a bit. Any ideas?
 

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Glad you got it figured out! Have no clue what the groaning noise after start up could be.
 

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2000 Silverado Z71 4x4 5.3L 460k+ miles w/ GM rebuilt motor and trans
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Could be the fuel pump bearing. I'm assuming it makes the sound after you turn the key...

If you turn the key to ON, but don't start the car, does it stop after a second or two?
 

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Oh yeah. Could be the fuel pump. Figured it was some kind of actuator kicking on then off?
 

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2000 Silverado Z71 4x4 5.3L 460k+ miles w/ GM rebuilt motor and trans
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Oh yeah. Could be the fuel pump. Figured it was some kind of actuator kicking on then off?
I don't know what else would be back there to come on? Unless the fan bearing for the rear AC (vent by the rear hatch, passenger side) is going and eventually turns off or is drowned out by road noise.
 
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